Reductase Deficiency Research Articles

Mycobacterium tuberculosis Thioredoxin Reductase Is Essential for Thiol Redox Homeostasis but Plays a Minor Role in Antioxidant Defense.

Mycobacterium tuberculosis (Mtb) must cope with exogenous oxidative stress imposed by the host. Unlike other antioxidant enzymes, Mtb’s thioredoxin reductase TrxB2 has been predicted to be essential not only to fight host defenses but also for in vitro growth. However, the specific physiological role of TrxB2 and its importance for Mtb pathogenesis remain undefined. Here we show that genetic inactivation of thioredoxin reductase perturbed several growth-essential processes, including sulfur and DNA metabolism and rapidly killed and lysed Mtb. Death was due to cidal thiol-specific oxidizing stress and prevented by a disulfide reductant. In contrast, thioredoxin reductase deficiency did not significantly increase susceptibility to oxidative and nitrosative stress. In vivo targeting TrxB2 eradicated Mtb during both acute and chronic phases of mouse infection. Deliberately leaky knockdown mutants identified the specificity of TrxB2 inhibitors and showed that partial inactivation of TrxB2 increased Mtb’s susceptibility to rifampicin. These studies reveal TrxB2 as essential thiol-reducing enzyme in Mtb in vitro and during infection, establish the value of targeting TrxB2, and provide tools to accelerate the development of TrxB2 inhibitors.

Pulmonary and Cerebral Infarcts Due to Secondary Thrombosis Risk of a Genetic Mutation: Life-threating Methylentetrahydrofolate Reductase (MTHFR) Deficiency with Early Onset

Abstract Methylentetrahydrofolate reductase (MTHFR) is a key enzymatic component of the folate cycle, converting 5,10-methylentetrahydrofolate into 5-methylentetrahydrofolate. Severe MTHFR deficiency is a rare recessive disease leading to major hyperhomocysteinemia, homocystinuria, and progressive neurological distress within the two first decades of life. We present the case of a young, 21 years old female patient who was admitted and treated in Clinic of Pneumology Tirgu Mures for a posterobasal left pneumonia without favourable radiologic evolution under antibiotic and symptomatic treatment. Thoracotomy was recommended in order to elucidate the diagnosis. The histopatological examination revealed the zone of pulmonary infarction. After 12 weeks from surgical intervention, the patient was admitted in Department of Neurology for stroke attack. The complex laboratory investigations reveal deficiency of methylentrahydrofolate reductase (MTHFR) caused by a genetic mutation.

Neurological Involvement in Tetrahydrobiopterin Deficiency

Tetrahydrobiopterin (BH4) is a natural and essential cofactor for the enzymatic hydroxylation of phenylalanine (Phe) and tyrosine (Tyr), and for two tryptophan hydroxylases, three nitric oxide synthases, and glyceryl-ether monooxygenase. Five separate genetic conditions affecting BH4 synthesis or recycling have been identified so far, including deficiency in (1) 6-pyruvoyltetrahydropterin synthase; (2) dihydropteridine reductase; (3) GTP cyclohydrolase I; (4) sepiapterin reductase; and (5) pterin-4α-carbinolamine dehydratase. These disorders cause hyperphenylalaninemia and impaired synthesis of serotonin and dopamine since tyrosine hydroxylase and neuronal tryptophan hydroxylase require BH4 and serotonin/dopamine products (5-hydroxytryptophan and L-dopa). All these five genetic conditions can be identified by newborn screening procedures due to elevated blood levels of Phe (with the sole exception of sepiapterin reductase deficiency). BH4 loading tests and measurement of neurotransmitter metabolites, pterins, and folates in cerebrospinal fluid can add further important information on disease severity. Untreated patients develop a complex neurological phenotype, which includes Parkinson-like features, brain degeneration, and early death. The gold standard treatment of severe disorders of BH4 metabolism is based on replacement therapy with BH4, 5-hydroxytryptophan, L-dopa, and carbidopa, with the addition, in certain cases, of folinic acid supplements and pramipexole. Dopamine agonists can improve L-dopa therapy, making treatment easier, relieving symptoms, stabilizing clinical course, and possibly ameliorating long-term outcomes. The outcome of patients with disorders of biopterin synthesis can be favorable, with either normal or near-normal cognition, and with some residual neurological symptoms usually manifesting diurnal variation, that is, worst when patients become tired or when the dosage or interval for medications is inadequate.

Mutation Update and Review of Severe Methylenetetrahydrofolate Reductase Deficiency.

Severe 5,10-methylenetetrahydrofolate reductase (MTHFR) deficiency is caused by mutations in the MTHFR gene and results in hyperhomocysteinemia and varying severity of disease, ranging from neonatal lethal to adult onset. Including those described here, 109 MTHFR mutations have been reported in 171 families, consisting of 70 missense mutations, 17 that primarily affect splicing, 11 nonsense mutations, seven small deletions, two no-stop mutations, one small duplication, and one large duplication. Only 36% of mutations recur in unrelated families, indicating that most are "private." The most common mutation is c.1530A>G (numbered from NM_005957.4, p.Lys510 = ) causing a splicing defect, found in 13 families; the most common missense mutation is c.1129C>T (p.Arg377Cys) identified in 10 families. To increase disease understanding, we report enzymatic activity, detected mutations, and clinical onset information (early, <1 year; or late, >1 year) for all published patients available, demonstrating that patients with early onset have less residual enzyme activity than those presenting later. We also review animal models, diagnostic approaches, clinical presentations, and treatment options. This is the first large review of mutations in MTHFR, highlighting the wide spectrum of disease-causing mutations.

5-α Reductase Deficiency in Two Siblings: A Case Report

A deficiency of 5-alpha reductase is a rare genetic disorder that affects 46,XY patients. The lack of enzyme causes inadequate differentiation of the gonads, leading to ambiguous genitalia or complete feminization of the external genitalia. Two sisters presented to their endocrinologist complaining of primary amenorrhea. Molecular studies revealed the SRD5A2 His231Arg gene mutation and karyotype showed 46,XY genotype. The diagnosis was supported by their high testosterone/dihydrotestosterone (DHT) ratio, response to the hCG stimulation test and their elevated sex hormone binding globulin (SHBG) levels. The siblings continued to identify as the female gender and were placed on oral premarin to develop secondary female sexual characteristics. In conclusion, any individual presenting with ambiguous genitalia, primary amenorrhea or virilization should be investigated for 5-alpha reductase deficiency by conducting a karyotype and full hormone profile. J Med Cases. 2016;7(7):263-265 doi: http://dx.doi.org/10.14740/jmc2482w

Treatment with Mefolinate (5-Methyltetrahydrofolate), but Not Folic Acid or Folinic Acid, Leads to Measurable 5-Methyltetrahydrofolate in Cerebrospinal Fluid in Methylenetetrahydrofolate Reductase Deficiency.

S-adenosyl methionine, which is formed from methionine, is an essential methyl donor within the central nervous system. Methionine is formed by the enzyme methionine synthase for which 5-methyltetrahydrofolate (5-MTHF) and homocysteine are substrates. Patients with severe methylenetetrahydrofolate reductase (MTHFR) deficiency cannot make 5-MTHF and have extremely low levels in the CSF. As a consequence, methylation reactions in the CNS are compromised, and this is likely to play an important role in the neurological abnormalities that occur in MTHFR deficiency. Although treatment with oral betaine can remethylate homocysteine to methionine in the liver, betaine crosses the blood-brain barrier poorly, and CSF levels of methionine remain low. We report three patients with severe MTHFR deficiency (enzyme activity ≤1% of controls) who had undetectable levels of CSF 5-MTHF at diagnosis and while on treatment with either folic acid or calcium folinate. Only treatment with oral 5-MTHF given as calcium mefolinate at doses of 15-60mg/kg/day resulted in an increase in CSF 5-MTHF.

Clinical, hormonal and radiological profile of 46XY disorders of sexual development.

Background and Objectives:46 XY disorders of sexual development (DSD) cover a wide spectrum of phenotypes ranging from unambiguous female genitalia to ambiguous male genitalia with hypospadias or dysgenetic gonads. Management of these patients depends on the cause of DSD, degree of feminization, age at presentation, and gender orientation. The aim of this study was to evaluate the presentation and management of patients with 46XY DSD at our center.Patients and Methods:All new and old patients of 46XY DSD attending the endocrine OPD in a period of 16 months were included in this study. Clinical, cytogenetic, hormonal, and radiological evaluation were done to identify the cause of DSD.Results:Among 19 patients, eight were diagnosed with disorders of gonadal development (one with complete gonadal dysgenesis, four with partial gonadal dysgenesis, two with congenital bilateral anorchia, and one with ovotesticular DSD) and eight with disorders of androgen synthesis and action (one with complete androgen insensitivity syndrome [AIS], three with partial AIS and four with 5α reductase deficiency). In three patients, a definitive diagnosis could not be made.Conclusions:Management of patients with DSD depends on etiology, gender assignment, gender orientation, hormonal treatment, genital surgery, and consequent psychosocial implications. Due to the overlapping clinical and biochemical parameters in different subsets of DSD, only a preliminary etiological diagnosis can be made in some cases. Genetic studies with long-term follow-up are required for an accurate diagnosis.

Gender identity and gender of rearing in 46 XY disorders of sexual development.

Background:Disorders of sexual development (DSD) may pose a challenge to live as a fully-functioning male or female. In this study, we prospectively assessed eleven 46 XY DSD patients who were being treated at our center over the last 8 months for gender dysphoria.Materials and Methods:To determine gender dysphoria, age-appropriate gender identity (GI) questionnaires were used. For patients, 12 years and below, parent report GI questionnaire for children was used and for those above 12 years of age, GI/gender dysphoria questionnaire for adolescents and adults was administered.Results:Of 11 patients with 46 XY DSD, three were diagnosed with 5 alpha reductase deficiency (5aRD), two with partial gonadal dysgenesis, three with partial androgen insensitivity syndrome, one each with ovotesticular, complete gonadal dysgenesis, and complete androgen insensitivity. Gender assigned at birth was female in eight and male in three patients. Among the eight reared as female, gender had been reassigned as male in three patients well before the present study was conducted. None of the eleven patients had gender dysphoria at the time of this study.Conclusion:Early gender of rearing was seen to be a critical indicator of present GI in our patients except in cases of 5aRD.

Effect of Cytochrome P450 Reductase Deficiency on 2-Amino-9H-pyrido[2,3-b]indole Metabolism and DNA Adduct Formation in Liver and Extrahepatic Tissues of Mice.

2-Amino-9H-pyrido[2,3-b]indole (AαC), a carcinogen formed during the combustion of tobacco and cooking of meat, undergoes cytochrome P450 (P450) metabolism to form the DNA adduct N-(deoxyguanosin-8-yl)-2-amino-9H-pyrido[2,3-b]indole (dG-C8-AαC). We evaluated the roles of P450 expressed in the liver and intestine to bioactivate AαC by employing male B6 wild-type (WT) mice, liver-specific P450 reductase (Cpr)-null (LCN) mice, and intestinal epithelium-specific Cpr-null (IECN) mice. Pharmacokinetic parameters were determined for AαC, 2-amino-9H-pyrido[2,3-b]indol-3-yl sulfate (AαC-3-OSO3H), and N(2)-(β-1-glucosidurony1)-2-amino-9H-pyrido[2,3-b]indole (AαC-N(2)-Glu) with animals dosed by gavage with AαC (13.6 mg/kg). The uptake of AαC was rapid with no difference in the plasma half-lives (t1/2) of AαC, AαC-3-OSO3H, and AαC-N(2)-Glu among mouse models. The maximal plasma concentrations (Cmax) and the areas under concentration-time curve (AUC0-24h) of AαC and AαC-N(2)-Glu were 4-24-fold higher in LCN than in WT mice, but they were not different between WT and IECN mice. These findings are consistent with the ablation of hepatic P450 activity in LCN mice. However, the Cmax and AUC0-24h of AαC-3-OSO3H in plasma were not substantially different among the mouse models. Similar pharmacokinetic parameters were obtained with WT and LCN mice treated with a lower AαC dose (1.36 mg kg(-1)). dG-C8-AαC was detected at similar levels in the livers of all three mouse models at the high AαC dose; levels of dG-C8-AαC in colon, bladder, and lung were greater in LCN than in WT mice and were the same in colon of IECN and WT mice. At the low AαC dose, dG-C8-AαC occurred at ∼ 40% lower levels in liver of LCN mouse than in WT mouse liver, but adduct levels remained higher in extrahepatic tissues of LCN mice. Therefore, hepatic P450 plays an important role in detoxication of AαC, but other hepatic or extrahepatic enzymes contribute to the bioactivation of AαC. P450s expressed in the intestine do not appreciably contribute to bioactivation of AαC in mice.

A novel nine base deletion mutation in NADH-cytochrome b5 reductase gene in an Indian family with recessive congenital methemoglobinemia-type-II

Recessive hereditary methemoglobinemia (RCM) associated with severe neurological abnormalities is a very rare disorder caused by NADH- cytochrome b5 reductase (cb5r) deficiency (Type II). We report a case of 11month old male child who had severe mental retardation, microcephaly and gross global developmental delay with methemoglobin level of 61.1%. The diagnosis of NADH-CYB5R3 deficiency was made by the demonstration of significantly reduced NADH-CYB5R3 activity in the patient and intermediate enzyme activity in both the parents. Mutation analysis of the CYB5R gene revealed a novel nine nucleotide deletion in exon 6 leading to the elimination of 3 amino acid residues (Lys173, Ser174 and Val 175). To confirm that this mutation was not an artifact, we performed PCR-RFLP analysis using the restriction enzyme Drd I. As the normal sequence has a restriction recognition site for Drd I which was eliminated by the deletion, a single band of 603-bp was seen in the presence of the homozygous mutation. Molecular modeling analysis showed a significant effect of these 3 amino acids deletion on the protein structure and stability leading to a severe clinical presentation. A novel homozygous 9 nucleotide deletion (p.K173–p.V175del3) is shown to be segregated with the disease in this family. Knowing the profile of mutations would allow us to offer prenatal diagnosis in families with severe neurological disorders associated with RCM — Type II.

Multidisciplinary approach and anesthetic management of a surgical cancer patient with methylene tetrahydrofolate reductase deficiency: a case report and review of the literature

IntroductionHyperhomocysteinemia is a known risk factor for myocardial infarction, stroke, peripheral vascular disease, and thrombosis. Elevated plasma homocysteine levels have been demonstrated in patients with recurrent episodes or a single episode of thrombosis. Here we describe the development of cardiovascular disease as a complication of a surgical intervention in a patient with colorectal cancer and hyperhomocysteinemia.Case presentationA 65-year-old Caucasian man complained of pain and constipation, attributed to previously diagnosed adenocarcinoma (stage IIB) of the hepatic flexure. An anamnestic investigation showed that he had undergone two surgical interventions. During both, he suffered thrombotic postoperative complications, a deep vein thrombosis of the upper extremity after the first operation and retinal vein occlusion after the second. He was diagnosed with hyperhomocysteinemia associated with a homozygous C677T mutation of the gene encoding the enzyme methylenetetrahydrofolate reductase. Our patient was initially treated with folic acid and high-dose B vitamins. On day 7 he underwent a right hemicolectomy. Anesthesia was performed with sevoflurane in 40% O2 and without the use of nitrous oxide. Postoperatively, our patient remained on folic acid and B vitamins and was without immediate or subsequent complications.ConclusionsNeoplastic disease and related surgery followed by the administration of chemotherapeutic drugs alter the hemostatic balance in cancer patients. Those suspected of also having a thrombophilic disease require a thorough laboratory diagnostic workup, including a molecular analysis aimed at identifying the genetic mutation responsible for the hyperhomocysteinemia, as indicated. The case described in this report highlights the importance of a multidisciplinary approach that includes expertise in peri-operative anesthesia, surgery, oncology, and hematology.

Estimation of reference curves for the urinary steroid metabolome in the first year of life in healthy children: Tracing the complexity of human postnatal steroidogenesis

ContextComplex steroid disorders such as P450 oxidoreductase deficiency or apparent cortisone reductase deficiency may be recognized by steroid profiling using chromatographic mass spectrometric methods. These methods are highly specific and sensitive, and provide a complete spectrum of steroid metabolites in a single measurement of one sample which makes them superior to immunoassays. The steroid metabolome during the fetal-neonatal transition is characterized by (a) the metabolites of the fetal-placental unit at birth, (b) the fetal adrenal androgens until its involution 3–6 months postnatally, and (c) the steroid metabolites produced by the developing endocrine organs. All these developmental events change the steroid metabolome in an age- and sex-dependent manner during the first year of life. ObjectiveThe aim of this study was to provide normative values for the urinary steroid metabolome of healthy newborns at short time intervals in the first year of life. MethodsWe conducted a prospective, longitudinal study to measure 67 urinary steroid metabolites in 21 male and 22 female term healthy newborn infants at 13 time-points from week 1 to week 49 of life. Urine samples were collected from newborn infants before discharge from hospital and from healthy infants at home. Steroid metabolites were measured by gas chromatography-mass spectrometry (GC–MS) and steroid concentrations corrected for urinary creatinine excretion were calculated. Results61 steroids showed age and 15 steroids sex specificity. Highest urinary steroid concentrations were found in both sexes for progesterone derivatives, in particular 20α-DH-5α-DH-progesterone, and for highly polar 6α-hydroxylated glucocorticoids. The steroids peaked at week 3 and decreased by ∼80% at week 25 in both sexes. The decline of progestins, androgens and estrogens was more pronounced than of glucocorticoids whereas the excretion of corticosterone and its metabolites and of mineralocorticoids remained constant during the first year of life. ConclusionThe urinary steroid profile changes dramatically during the first year of life and correlates with the physiologic developmental changes during the fetal-neonatal transition. Thus detailed normative data during this time period permit the use of steroid profiling as a powerful diagnostic tool.

The Spectrum of Early Movement Disorders in Congenital Defects of Biogenic Amine Metabolism

This article analyzes the pattern of movement disorders in children with primary defects of biogenic amine metabolism emerging during the first 3 year of life. A PubMed search was performed using the keywords “monoamine neurotransmitter disorders,” “congenital defects of biogenic amine metabolism,” “early onset movement disorders,” “autosomal dominant guanosine-triphosphate-cyclohydrolase deficiency,” “autosomal recessive guanosine-tryphosphate-cyclohydrolase deficiency,” “6-pyruvoyl-tethrahydropterin synthase deficiency,” “sepiapterin reductase deficiency,” “dihydropteridine reductase deficiency,” “tyrosine hydroxilase deficiency,” “aromatic l-amino acid decarboxylase deficiency,” “dopamine transporter deficiency,” and “vesicular monoamine transporter 2.” A personal series of 27 patients affected by these disorders was presented and discussed. Primary defects of biogenic amine metabolism result in a spectrum of movement disorders associated with derangement of postural reaction and global development delay. Movement disorders virtually represent the presentation symptoms in most of these diseases. The prominent early clinical patterns of movement disorders are akinesia (with rigidity or hypotonia) and hyperkinesia (dystonia, myoclonic jerks, and tremor). While some diseases present with a rather stereotyped clinical pattern (i.e., Aromatic l -amino acid decarboxylase, sepiapterin reductase, and Dopamine transporter deficiencies), others (i.e., Guanosine-triphosphate-cyclohydrolase, 6-pyruvoyl tetrahydropterin synthase, dihydropteridine reductase, and tyrosine hydroxylase deficiencies) may present with more pleomorphic features. As a general rule, earlier the onset of the disease is, more severe and generalized is the derangement of motor functions. Inherited disorders of monoamine neurotransmitter metabolism include the few idiopathic movement disorders with the possibility of etiological treatments. For these reasons, they should always be considered in the diagnostic work-up of children with early onset movement disorders.

Diagnosis of Biogenic Amines Synthesis Defects

Defects of biogenic amines synthesis encompass a group of rare genetic disorders that have been described during the last few decades. They include tyrosine hydroxylase deficiency, aromatic L-amino acid decarboxylase deficiency, and pterin defects such as 6-pyruvoyl-tetrahydropterin synthase deficiency, dihydropteridine reductase deficiency, guanosine triphosphate cyclohydrolase-I deficiency, and sepiapterin reductase deficiency. These diseases cause low brain concentrations of catecholamines (dopamine and norepinephrine) and serotonin, which may affect motor, cognitive, and autonomic nervous system. Although most patients have recognizable phenotypes, and share a collection of overlapping symptoms, presentations vary widely and may appear to be nonclassic for the specific disorder. In general, the spectrum of clinical manifestations range from benign forms such as L-3,4-dihydroxyphenylalanine responsive movement disorders to severe encephalopathies that are difficult to treat. These conditions require the specialized analysis of the cerebrospinal fluid because every defect has a very suggestive profile in regard to monoamine and pterin metabolites. However, secondary deficiencies of these metabolites in the cerebrospinal fluid can also be found in a wide variety of neurological disorders. Owing to the still existing challenges of the diagnostic approach, it is important to highlight some of the most relevant clinical and biochemical signatures, as well as to propose practical algorithms that may help clinicians to detect and treat these patients.

A case of severe methylenetetrahydrofolate reductase deficiency presenting as neonatal encephalopathy, seizures, microcephaly and central hypoventilation

Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in the remethylation of homocysteine to methionine. S-adenosylmethionine, formed from methionine and adenosine triphosphate, is the methyl donor in crucial reactions for brain development and function. MTHFR deficiency is the most prevalent inborn error of folate metabolism and is characterized by hyperhomocysteinemia and hypomethioninemia. A broad clinical spectrum includes psychomotor retardation, microcephaly, seizures, central respiratory failure and death. Premature atherosclerosis, arterial and venous thrombosis or psychiatric manifestations occur in the late onset forms. We report a female neonate with severe MTHFR deficiency presenting with neonatal encephalopathy, congenital microcephaly, seizures, central hypoventilation with gross cerebral atrophy, hypomyelination and pontine hypoplasia on magnetic resonance imaging of brain. She succumbed at 10 wk of age despite treatment with oral S-adenosylmethionine, betaine, folinic acid, riboflavin and hydroxycobalamin. © 2013 - IOS Press and the authors. All rights reserved.

Urine sepiapterin excretion as a new diagnostic marker for sepiapterin reductase deficiency

Sepiapterin reductase deficiency (SRD) causes depletion of biogenic amines in the brain, early onset motor disorder, and intellectual disability. The diagnostic marker for this rare disease is increased sepiapterin and biopterin in CSF. Through a new analytic methodology we demonstrated accumulation of sepiapterin in urine of four SRD patients several times greater than that found in healthy controls and carriers, regardless of age or treatment. Our findings suggest a new interpretation of current theories of peripheral pterin metabolism and provide a new noninvasive diagnostic tool for children with early onset cryptogenetic developmental delay and/or movement disorder.

Clinical pattern, mutations and in vitro residual activity in 33 patients with severe 5, 10 methylenetetrahydrofolate reductase (MTHFR) deficiency.

Severe methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare inborn defect disturbing the remethylation of homocysteine to methionine (<200 reported cases). This retrospective study evaluates clinical, biochemical genetic and in vitro enzymatic data in a cohort of 33 patients. Clinical, biochemical and treatment data was obtained from physicians by using a questionnaire. MTHFR activity was measured in primary fibroblasts; genomic DNA was extracted from cultured fibroblasts. Thirty-three patients (mean age at follow-up 11.4 years; four deceased; median age at first presentation 5 weeks; 17 females) were included. Patients with very low (<1.5%) mean control values of enzyme activity (n = 14) presented earlier and with a pattern of feeding problems, encephalopathy, muscular hypotonia, neurocognitive impairment, apnoea, hydrocephalus, microcephaly and epilepsy. Patients with higher (>1.7-34.8%) residual enzyme activity had mainly psychiatric symptoms, mental retardation, myelopathy, ataxia and spasticity. Treatment with various combinations of betaine, methionine, folate and cobalamin improved the biochemical and clinical phenotype. During the disease course, patients with very low enzyme activity showed a progression of feeding problems, neurological symptoms, mental retardation, and psychiatric disease while in patients with higher residual enzyme activity, myelopathy, ataxia and spasticity increased. All other symptoms remained stable or improved in both groups upon treatment as did brain imaging in some cases. No clear genotype-phenotype correlation was obvious. MTHFR deficiency is a severe disease primarily affecting the central nervous system. Age at presentation and clinical pattern are correlated with residual enzyme activity. Treatment alleviates biochemical abnormalities and clinical symptoms partially.

Methionine synthase reductase deficiency (CblE): A report of two patients and a novel mutation

Importance: Functional methionine synthase reductase deficiency, also known as cobalamin E disorder, is a rare autosomal recessive inherited disease that results in an impaired remethylation of homocysteine to methionine. It presents with macrocytic anemia, hyperhomocysteinemia, and hypomethioninemia, and may also be accompanied with neurological impairment.Clinical presentation: We describe two new cases of unrelated girls with megaloblastic anemia misclassified at first as congenital dyserythropoietic anemia with development of neurologic dysfunction in one of them.Intervention: The posterior finding of biochemical features (hyperhomocysteinemia and hypomethioninemia) focused the diagnosis on the inborn errors of intracellular vitamin B12. Subsequent molecular analysis of the methionine synthase reductase (MTRR) gene revealed compound heterozygosity for a transition c.1361C > T (p.Ser454Leu) and another, not yet described in literature, c.1677–1G > A (p.Glu560fs) in one patient, and a single homozygosis mutation, c.1361C > T (p.Ser545Leu) in the other one. These mutations confirmed the diagnosis of cobalamin E deficiency.Conclusion: Treatment with hydroxocobalamin in combination with betaine appears to be useful for hematological improvement and prevention of brain disabilities in CblE-affected patients. Our study widens the clinical, molecular, metabolic, and cytological knowledge of deficiency MTRR enzyme.

Insights into severe 5,10-methylenetetrahydrofolate reductase deficiency: molecular genetic and enzymatic characterization of 76 patients.

5,10-Methylenetetrahydrofolate reductase (MTHFR) deficiency is the most common inherited disorder of folate metabolism and causes severe hyperhomocysteinaemia. To better understand the relationship between mutation and function, we performed molecular genetic analysis of 76 MTHFR deficient patients, followed by extensive enzymatic characterization of fibroblasts from 72 of these. A deleterious mutation was detected on each of the 152 patient alleles, with one allele harboring two mutations. Sixty five different mutations (42 novel) were detected, including a common splicing mutation (c.1542G>A) found in 21 alleles. Using an enzyme assay in the physiological direction, we found residual activity (1.7%-42% of control) in 42 cell lines, of which 28 showed reduced affinity for nicotinamide adenine dinucleotide phosphate (NADPH), one reduced affinity for methylenetetrahydrofolate, five flavin adenine dinucleotide-responsiveness, and 24 abnormal kinetics of S-adenosylmethionine inhibition. Missense mutations causing virtually absent activity were found exclusively in the N-terminal catalytic domain, whereas missense mutations in the C-terminal regulatory domain caused decreased NADPH binding and disturbed inhibition by S-adenosylmethionine. Characterization of patients in this way provides a basis for improved diagnosis using expanded enzymatic criteria, increases understanding of the molecular basis of MTHFR dysfunction, and points to the possible role of cofactor or substrate in the treatment of patients with specific mutations.

In memoriam: S. Harvey Mudd.

S. Harvey Mudd died January 21, 2014, succumbing to pneumonia after heart surgery. On hearing of his death a colleague noted “We have lost a generation of Biochemistry in a single man”. Harvey was the acknowledged international authority on diseases of methionine metabolism. He wrote the chapters on methionine and sulfur metabolism in the last four editions of “Metabolic Basis of Inherited Disease”, a source of information used world-wide. Physicians all over the world suspecting a metabolic defect involving methionine in a patient would routinely consult him and send samples for analysis. His devotion to discovering the underlying reasons for the patient’s complications was legendary. Dr. Mudd was born in 1927 in Bryn Mawr, Pennsylvania. He grew up in an academic family and signed his papers S. Harvey Mudd in order to distinguish himself from his father, Stuart Mudd, also a well-known scientist who served as Chairman of the Department of Microbiology at the University of Pennsylvania. His mother, Dr. Emily B. H. Mudd, founded the Marriage Council of Philadelphia and was a Professor in the Department of Psychiatry, also at the University of Pennsylvania. After high school Harvey enlisted in the Navy in 1945. Soon after the Second World War ended he was discharged, having served less than a year. He attended Harvard University and graduated cum laude with an AB degree in 1949. A formative influence on his lifelong commitment to science was the following summer he spent as a student in the laboratory of Dr. George Wald. Wald was a spellbinding speaker and inspirational teacher who subsequently received the Nobel Prize in 1967 for his work on the pigments of the eye and the role of vitamin A in vision. Following this, Harvey entered Harvard Medical School and managed to spend the summer of 1950 in the laboratory of another Nobel laureate, Fritz Lipmann. Lipmann was a brilliant and innovative thinker who conceived the concept of high-energy bonds in biochemistry and also discovered Coenzyme A. In 1953 Harvey received an M.D. degree from Harvard and then completed his internship at Massachusetts General Hospital. He then returned to Lipmann’s laboratory as a Research Fellow for two years where he studied the uncoupling of oxidative phosphorylation. It was during this time he met and married Marion Heinrich in 1955. Because Harvey’s initial period in the Navy was less than one year, he was subject to the draft of M.D.s that was in place during the Korean War. At that time a limited number of newly graduated M.D.s were selected to serve in the Public Health Service at the National Institutes of Health, a much sought after position. Harvey was selected to work in the laboratory of Dr. Giulio Cantoni in 1956 and remained at NIH for his entire career. Dr. Cantoni was the discoverer of S-adenosylmethionine (AdoMet), the principal doHow to Cite this Article: Blom HJ,Stabler S, Wagner C. 2015. In Memoriam: S. Harvey Mudd.