Recombinant Human Enzyme Research Articles

Final results of the phase 1/2, open-label clinical study of intravenous recombinant human N-acetyl-α-d-glucosaminidase (SBC-103) in children with mucopolysaccharidosis IIIB

Mucopolysaccharidosis IIIB is caused by a marked decrease in N-acetyl-α-d-glucosaminidase (NAGLU) enzyme activity, which leads to the accumulation of heparan sulfate in key organs, progressive brain atrophy, and neurocognitive decline. In this open-label study, 11 eligible patients aged 2 to <12 years (developmental age ≥ 1 year) were sequentially allocated to recombinant human NAGLU enzyme (SBC-103) in 3 staggered- and escalating-dose groups (0.3 mg/kg [n = 3], 1.0 mg/kg [n = 4], or 3.0 mg/kg [n = 4]) by intravenous infusion every 2 weeks for 24 weeks, followed by a 4-week interruption (Part A), treatment at 1.0 and/or 3.0 mg/kg every 2 weeks starting at week 28 (Part B), and treatment at 5.0 or 10.0 mg/kg every 2 weeks (Part C) for approximately 2 total years in the study. The primary objective of the study was safety and tolerability evaluation; secondary objectives included evaluation of SBC-103 effects on total heparan sulfate levels in cerebrospinal fluid (CSF), brain structural magnetic resonance imaging (cortical gray matter volume), and neurocognitive status (age equivalent/developmental quotient). During the study, 13 treatment-emergent serious adverse events (SAEs) occurred in 3 patients; 32 infusion-associated reactions (IARs) occurred in 8 patients. Most AEs were mild and intravenous treatment with SBC-103 was well tolerated. Mean (SD) changes from baseline at 52 weeks in Part C for the 5.0 and 10.0 mg/kg doses, respectively, were: −4.7% (8.3) and − 4.7% (14.7) for heparan sulfate levels in CSF, −8.1% (3.5) and − 10.3% (9.4) for cortical gray matter volume, +2.3 (6.9) points and +1.0 (9.2) points in cognitive age equivalent and −8.9 (10.2) points and −14.4 (9.2) points in developmental quotient. In summary, SBC-103 was generally well tolerated. Changes in heparan sulfate levels in CSF were small and were not maintained from earlier study time points, there was no clear evidence overall of clinically meaningful improvement in neurocognitive function at the higher doses investigated, and no dose-dependent effects were observed.

Pharmacokinetics (PK) of Subcutaneous Daratumumab in Patients with Relapsed or Refractory (RR) Multiple Myeloma (MM): Primary Clinical Pharmacology Analysis of the Open-Label, Multicenter, Phase 1b Study (PAVO)

Pharmacokinetics (PK) of Subcutaneous Daratumumab in Patients with Relapsed or Refractory (RR) Multiple Myeloma (MM): Primary Clinical Pharmacology Analysis of the Open-Label, Multicenter, Phase 1b Study (PAVO)

Subcutaneous Daratumumab in Patients with Relapsed or Refractory Multiple Myeloma: Part 2 Safety and Efficacy Update of the Open-Label, Multicenter, Phase 1b Study (PAVO)

Subcutaneous Daratumumab in Patients with Relapsed or Refractory Multiple Myeloma: Part 2 Safety and Efficacy Update of the Open-Label, Multicenter, Phase 1b Study (PAVO)

Metabolism and Bioactivation of Corynoline With Characterization of the Glutathione/Cysteine Conjugate and Evaluation of Its Hepatotoxicity in Mice.

Corynoline (CRL), an isoquinoline alkaloid, is the major constituent derived from Corydalis bungeana Herba, which is a well-known Chinese herbal medicine widely used in many prescriptions. The purpose of this study was to comprehensively investigate the metabolism and bioactivation of CRL, and identify the CYP450 isoforms involved in reactive ortho-benzoquinone metabolites formation and evaluate its hepatotoxicity in mice. Here, high resolution and triple quadrupole mass spectrometry were used for studying the metabolism of CRL. Three metabolites (M1–M3) and four glutathione conjugates (M4–M7) of CRL ortho-benzoquinone reactive metabolite were found in vitro using rat and human liver microsomes supplemented with NADPH and glutathione. Four cysteine conjugates (M8–M11) were trapped in mice besides M1–M7. Using human recombinant CYP450 enzymes and chemical inhibitor method, we found that CYP3A4, CYP2C19, CYP2C9, and CYP2D6 were mainly involved in the bioactivation of CRL. Furthermore, CRL had no obvious hepatotoxicity and did not induce acute liver injuries in the experimental dosage (125–500 mg/kg) used in this study. However, phenomena of abnormal behaviors and low body temperature appeared in mice after drug administration, and three of them were dead. Tissue distribution study of CRL in mice showed that the main target organ of CRL was liver, then kidney, heart, and brain. CRL could traverse the blood–brain barrier, and have relative high concentration in brain. So, we surmise that toxicity effect of CRL on other organs may have occurred, and more attention should be paid on the traditional Chinese medicine contained CRL in clinic.

Nonclinical pharmacokinetics and in vitro metabolism of H3B-6545, a novel selective ERα covalent antagonist (SERCA).

H3B-6545, a novel selective estrogen receptor (ER)α covalent antagonist (SERCA) which inactivates both wild-type and mutant ERα, is in clinical development for the treatment of metastatic breast cancer. Preclinical studies were conducted to characterize the pharmacokinetics and metabolism of H3B-6545 in rat and monkeys. The clearance and metabolic profiles of H3B-6545 were studied using rat, monkey and human hepatocytes, and reaction phenotyping was done using recombinant human cytochrome P450 enzymes. Blood stability, protein binding, and permeability were also determined in vitro. Pharmacokinetics of H3B-6545 was assessed after both intravenous and oral dosing. A nonclinical PBPK model was developed to assess in vitro-in vivo correlation of clearance. H3B-6545 had a terminal elimination half-life of 2.4h in rats and 4.0h in monkeys and showed low to moderate bioavailability, in line with the in vitro permeability assessment. Plasma protein binding was similar across species, at 99.5-99.8%. Nine metabolites of H3B-6545 were identified in hepatocyte incubations, none of which were unique to humans. Formation of glutathione-related conjugate of H3B-6545 was minimal in vitro. H3B-6545, a CYP3A substrate, is expected to be mostly cleared via hepatic phase 1 metabolism. Hepatocyte clearance values were used to adequately model the time-concentration profiles in rat and monkey. We report on the absorption and metabolic fate and disposition of H3B-6545 in rats and dogs and illustrate that in vitro-in vivo correlation of clearance is possible for targeted covalent inhibitors, provided reactivity is not a predominant mechanism of clearance.

The metabolism and hepatotoxicity of ginkgolic acid (17 : 1) in vitro

Pharmacological activities and adverse side effects of ginkgolic acids (GAs), major components in extracts from the leaves and seed coats of Ginkgo biloba L, have been intensively studied. However, there are few reports on their hepatotoxicity. In the present study, the metabolism and hepatotoxicity of GA (17 : 1), one of the most abundant components of GAs, were investigated. Kinetic analysis indicated that human and rat liver microsomes shared similar metabolic characteristics of GA (17 : 1) in phase I and II metabolisms. The drug-metabolizing enzymes involved in GA (17 : 1) metabolism were human CYP1A2, CYP3A4, UGT1A6, UGT1A9, and UGT2B15, which were confirmed with an inhibition study of human liver microsomes and recombinant enzymes. The MTT assays indicated that the cytotoxicity of GA (17 : 1) in HepG2 cells occurred in a time- and dose-dependent manner. Further investigation showed that GA (17 : 1) had less cytotoxicity in primary rat hepatocytes than in HepG2 cells and that the toxicity was enhanced through CYP1A- and CYP3A-mediated metabolism.

Endocrine activities and adipogenic effects of bisphenol AF and its main metabolite

Bisphenol AF (BPAF) is a fluorinated analog of bisphenol A (BPA), and it is a more potent estrogen receptor (ER) agonist. BPAF is mainly metabolized to BPAF-glucuronide (BPAF-G), which has been reported to lack ER agonist activity and is believed to be biologically inactive. The main goal of the current study was to examine the influence of the metabolism of BPAF via glucuronidation on its ER activity and adipogenesis. Also, as metabolites can have different biological activities, the effects of BPAF-G on other nuclear receptors were evaluated. First, in-vitro BPAF glucuronidation was investigated using recombinant human enzymes. Specific reporter-gene assays were used to determine BPAF and BPAF-G effects on estrogen, androgen, glucocorticoid, and thyroid receptor pathways, and on PXR, FXR, and PPARγ pathways. Their effects on lipid accumulation and differentiation were determined in murine 3T3L1 preadipocytes using Nile Red, with mRNA expression analysis of the adipogenic markers adiponectin, Fabp4, Cebpα, and PPARγ. BPAF showed strong agonistic activity for hERα and moderate antagonistic activities for androgen and thyroid receptors, and for PXR. BPAF-G was antagonistic for PXR and PPARγ. BPAF (0.1 μM) and BPAF-G (1.0 μM) induced lipid accumulation and increased expression of key adipogenic markers in murine preadipocytes. BPAF-G is therefore not an inactive metabolite of BPAF. Further toxicological and epidemiological investigations of BPAF effects on human health are warranted, to provide better understanding of the metabolic end-elimination of BPAF.

The use of PBPK modeling across the pediatric age range using propofol as a case.

The project SAFEPEDRUG aims to provide guidelines for drug research in children, based on bottom-up and top-down approaches. Propofol, one of the studied model compounds, was selected because it is extensively metabolized in liver and kidney, with an important role for the glucuronidation pathway. Besides, being a lipophilic molecule, it is distributed into fat tissues, from where it redistributes into the systemic circulation. In the past, both bottom-up (Physiologically based pharmacokinetic, PBPK) and top-down approaches (population pharmacokinetic, popPK) were applied to describe its pharmacokinetics (PK). In this work, a combination of the two was used to check their performance to describe PK in children and neonates (both term and preterm) using propofol as a case compound. First, in vitro data was generated in human liver microsomes and recombinant enzymes and used to develop an adult PBPK model in Simcyp®. Activity adjustment factors (AAFs) were calculated to account for differences between in vitro and in vivo enzyme activity. Clinical data were analyzed using a 3-compartment model in NONMEM. These data were used to construct a retrograde PBPK model and for qualification of the PBPK models. Once an accurate in vivo clearance was obtained accounting for the contribution of the different metabolic pathways, the resulting PBPK models were challenged with new data for qualification. After that, the constructed adult PPBK model for propofol was extrapolated to the pediatric population. Both the default built-in and in vivo derived ontogeny functions were used to do so. The models were qualified by comparing their predicted PK parameters to published values, and by comparison of predicted concentration-time profiles to available clinical data. Clearance values were predicted well, especially when compared with values obtained from trials where long-term sampling was applied, whereas volume of distribution was lower compared to the most common popPK model predictions. Concentration-time profiles were predicted well up until and including the preterm neonatal population. In this work, it was thus shown that PBPK can be used to predict the PK up to and including the preterm neonatal population without the use of pediatric in vivo data. This work adds weight to the need for further development of PBPK models, especially regarding distribution modeling and the use of in vivo derived ontogeny functions.

Discovery of rubiarbonone C as a selective inhibitor of cytochrome P450 4F enzymes.

Cytochrome P450 (CYP) enzymes, particularly CYP4A/4F, are the major ω-hydroxylases of arachidonic acid (AA) that can produce 20-hydroxyeicosatetraenoic acid (20-HETE). Although there are dissimilarities in substrate specificity, tissue distribution, and gene regulation between CYP4A and CYP4F, selective CYP4A or 4F inhibitors are currently unavailable. Therefore, this study was designed to develop CYP4F selective inhibitors using a novel inhibitory assay of 20-HETE formation. The assay was established using pooled human kidney microsomes (HKMs) and human recombinant CYP4 enzymes incubated with 1,2,3,4,5-13C AA (13C5 AA) as a substrate to minimize interference by endogenous AA. The intrinsic clearance (Vmax/Km) values were 9.5µL/min/mg for HKMs and 0.02, 0.9, and 10.1µL/min/pmol for CYP4A11, CYP4F2, and CYP4F3B, respectively, which suggests a major role for CYP4F in ω-hydroxylation of AA. To validate the assay, we tested well-known pan-CYP4 inhibitor HET0016 along with 50 compounds derived from natural products. Of the screened compounds, rubiarbonone C showed the most potent inhibitory activity. The 50% inhibitory concentrations of rubiarbonone C against CYP4A11, CYP4F2, and 4F3B were > 50, 4.2, and 4.2µM, respectively. Moreover, epoxyeicosatrienoic acid formation from 13C5 AA was not inhibited by up to 30µM rubiarbonone C. Meanwhile, in pooled human liver microsomes, CYP1, 2, and 3 family enzymes involved in drug metabolism were not substantially inhibited by rubiarbonone C. Thus, rubiarbonone C is a selective inhibitor of CYP4F and can be used to discriminate among CYP4 family enzymes and evaluate their roles in physiological and pathophysiological conditions.

36-Months follow-up assessment after cessation and resuming of enzyme replacement therapy in late onset Pompe disease: data from the Swiss Pompe Registry.

Although not curative, enzyme replacement therapy (ERT) with recombinant human acid alpha-glucosidase enzyme has shown to be effective in the treatment of late-onset Pompe disease (LOPD). For this potentially life-long treatment, little is known on the clinical effect of cessation and resuming ERT. Due to a Swiss supreme court decision on ERT reimbursement, a temporary stop of ERT occurred in our study population. The aim of this study was to report the 36-months follow-up assessments after resuming ERT. After resuming ERT, seven patients suffering from genetically and enzymatically confirmed LOPD had periodic, mandatory, prospective assessments of pulmonary function tests, muscle strength summary scores, distances walked in timed walking tests, and patient-reported questionnaires. Data were statistically analyzed for significant differences between time points at ERT cessation, at ERT resuming, and 36 months thereafter. After resuming ERT forced vital capacity (p = 0.007) and distance walked in the 6min walk test (6-MWT, p = 0.011) significantly increased at 36 months. Compared to before ERT cessation, distance walked in 6-MWT at 36 months still remained significantly lower (p = 0.005). Self-reported scores in the fatigue severity scale significantly declined at 36 months after resuming ERT (p = 0.019). No other functional or reported parameter significantly changed at 36 months after resuming ERT. Our data suggests that long-term interruption of ERT in LOPD may lead to deterioration of clinical meaningful parameters and quality of life. In addition, a clinical restoration after ERT cessation is possible for most of the LOPD patients within a 36 months follow-up.

Quinone and nitrofurantoin redox cycling by recombinant cytochrome b5 reductase

NADH cytochrome b5 reductase mediates electron transfer from NADH to cytochrome b5 utilizing flavin adenine dinucleotide as a redox cofactor. Reduced cytochrome b5 is an important cofactor in many metabolic reactions including cytochrome P450-mediated xenobiotic metabolism, steroid biosynthesis and fatty acid metabolism, hemoglobin reduction, and methionine and plasmalogen synthesis. Using recombinant human enzyme, we discovered that cytochrome b5 reductase mediates redox cycling of a variety of quinones generating superoxide anion, hydrogen peroxide, and, in the presence of transition metals, hydroxyl radicals. Redox cycling activity was oxygen-dependent and preferentially utilized NADH as a co-substrate; NADH was 5–10 times more active than NADPH in supporting redox cycling. Redox cycling activity was greatest for 9,10-phenanthrenequinone and 1,2-naphthoquinone, followed by 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone (menadione), nitrofurantoin and 2-hydroxyestradiol. Using menadione as the substrate, quinone redox cycling was found to inhibit reduction of cytochrome b5 by cytochrome b5 reductase, as measured by heme spectral changes in cytochrome b5. Under anaerobic conditions where redox cycling is inhibited, menadione had no effect on the reduction of cytochrome b5. Chemical redox cycling by cytochrome b5 reductase may be important in generating cytotoxic reactive oxygen species in target tissues. This activity, together with the inhibition of cytochrome b5 reduction by redox-active chemicals and consequent deficiencies in available cellular cytochrome b5, are likely to contribute to tissue injury following exposure to quinones and related redox active chemicals.

NEW THERAPEUTIC APPROACHES AND THEIR READOUT: O.20Results from ATB200-02: first-in-human, open-label, phase 1/2 study of ATB200 co-administered with AT2221 for Pompe disease

Late-onset Pompe disease (LOPD) is caused by impaired lysosomal glycogen clearance due to acid alpha-glucosidase (GAA) deficiency. Accumulation of glycogen in skeletal muscle and diaphragm leads to loss of muscle and respiratory function. Recombinant human GAA enzyme replacement therapy (rhGAA ERT; alglucosidase alfa) is standard treatment for LOPD. ATB200-02 (NCT02675465) is a first-in-human, open-label, Phase 1/2 trial to evaluate ATB200, a next-generation rhGAA ERT, co-administered with AT2221, an oral pharmacological chaperone, in adults with LOPD. Twenty patients (pts) were enrolled: ERT-switch ambulatory (Cohort 1, n=11), ERT-switch nonambulatory (Cohort 2, n=4), and ERT-naive ambulatory (Cohort 3, n=5). Mean±SD 6-minute walk test increased for ambulatory ERT-switch (Month [Mo] 6 [n=10], +23.9±52.2; Mo 9 [n=10], +24.5±40.8; Mo 12 [n=8], +57.4±34.4 m) and ERT-naive pts (Mo 6 [n=5], +41.8±29.4; Mo 9 [n=5], +63.5±23.1; Mo 12 [n=2], +86.8±11.1 m). Other motor function tests were generally consistent with these results. Increases were observed in upper extremity strength in nonambulatory ERT-switch pts at Mo 6 and 9. Forced vital capacity (% predicted) increased in ERT-naive pts (Mo 6 [n=5], +4.2; Mo 9 [n=5], +6.2; Mo 12 [n=2], +6.0) and was generally stable in ambulatory ERT-switch pts (Mo 6 [n=9], -1.3; Mo 9 [n=9], -1.7; Mo 12 [n=7], -3.1). All cohorts demonstrated improvements in the Fatigue Severity Scale. ATB200/AT2221 was associated with reductions in creatine kinase and urine hexose tetrasaccharide. The most common treatment-emergent adverse events were upper and lower abdominal pain (n=8), diarrhea (n=8), and nasopharyngitis (n=6). Three events of infusion-associated reactions occurred in 550+ infusions. Data from this interim analysis show a clinical benefit of ATB200/AT2221 in ERT-naive pts and in pts who have been on ERT for ∼5 years. ATB200/AT2221 has the potential to be a significant treatment alternative for patients with Pompe disease.

Interaction between 3,4‑dichlorophenyl‑propenoyl‑sec.‑butylamine (3,4‑DCPB), an antiepileptic drug, and cytochrome P450 in rat liver microsomes and recombinant human enzymes in vitro

The compound 3,4‑dichlorophenyl‑propenoyl‑sec.‑butylamine (3,4‑DCPB) is an antiepileptic drug. The purpose of the present research was to identify cytochrome P450 (CYP450) responsible for the metabolism of 3,4‑DCPB and evaluate the effects of 3,4‑DCPB on the activities of CYP450 enzymes. 3,4‑DCPB was incubated with rat liver microsomes (RLMs) plus six CYP450 enzyme-specific inhibitors, or six recombinant human CYP450 enzymes (rhCYP450s). The concentrations of 3,4‑DCPB and six CYP450 enzyme-activities probe drugs were detected by high-performance liquid chromatographic (HPLC). The results showed that the prototype of 3,4‑DCPB was metabolized by multiple CYP450 enzymes into three metabolites, and the predominant isoforms were CYP2D6 (metabolite M1), CYP1A2 (M2), CYP2C19 and CYP3A4 (M3), respectively., in the presence of β-NADPH (1 mM) in RLMs or rhCYP450s. Compared with the control (PB−), phenobarbital pre-treatment (PB+) significantly enhanced levels (all of p < 0.01) of hydroxylmethytobutamide (CYP2C9), 4‑hydroxy‑mephenytoin (CYP2C19), acetaminophen (CYP1A2), 6‑hydroxychlorzoxazone (CYP2E1) and oxidized nifedipine (CYP3A4), respectively, in spite of dextrophan (CYP2D6) was not markedly enhanced in RLMs. Conversely, the inhibitory ratios of 3,4‑DCPB (16 μg/mL, 59 μM) on the activities of CYP2C9, CYP2C19, CYP1A2 and CYP2D6 were 97.6%, 59.0%, 53.5% and 36.5%, respectively. However, CYP2E1 (both of PB− and PB+) and CYP3A4 (PB+) were not inhibited by 3,4‑DCPB in RLMs. In conclusion, the present study showed that 3,4‑DCPB was metabolized by multiple CYP450 enzymes. 3,4‑DCPB inhibited the activities of CYP2C9, CYP2C19, CYP1A2 and CYP2D6, rather than that CYP2E1 and CYP3A4 enzymes, suggesting that the different effects of 3,4‑DCPB on the CYP450 enzymes might influence metabolic drug-drug interaction in antiepileptics therapy.

Bromo-dragonfly, a psychoactive benzodifuran, is resistant to hepatic metabolism and potently inhibits monoamine oxidase A

Bromo-dragonfly is a benzodifuran derivative known as one of the most potent 5-HT2A-receptor agonists within this chemical class, with long-lasting effects of up to 2–3 days. In addition to hallucinogenic effects, the drug is a potent vasoconstrictor, resulting in severe adverse effects, such as necrosis of the limbs. In some cases, intoxication has had fatal outcomes. Little is known about the metabolism of bromo-dragonfly. The aims of this study were to investigate the pharmacokinetics of bromo-dragonfly, determine the plasma protein binding, examine the human hepatic metabolism in vitro, and compare with those of its close analogue, 2C-B-fly. Additionally, we assayed the inhibition potency of both compounds on the monoamine oxidase (MAO) A- and B-mediated oxidative deamination of serotonin (5-HT) and dopamine, respectively. Liquid chromatography high-resolution mass spectrometry was used for metabolism studies in pooled human liver microsomes (HLM), pooled human liver cytosol (HLC) and recombinant enzymes. Inhibition studies of the deamination of 5-HT and dopamine were carried out using LC–MS/MS. Bromo-dragonfly was not metabolised in the tested in vitro systems. On the other hand, 2C-B-fly was metabolised in HLM by CYP2D6 and in HLC to some extent, with the main biotransformations being monohydroxylation and N-acetylation. Furthermore, MAO-A metabolised 2C-B-fly, producing the aldehyde metabolite, which was trapped in vitro with methoxyamine. Inhibition experiments revealed that bromo-dragonfly is a competitive inhibitor of MAO-A with a Ki of 0.352 μM. The IC50 value for bromo-dragonfly indicated that the inhibition of MAO-A may be clinically relevant. However, more data are needed to estimate its impact on the increase of 5-HT in vivo.

Synthesis and Evaluation of 2-benzylidene-1-tetralone Derivatives for Monoamine Oxidase Inhibitory Activity.

Chalcone has been identified as a promising lead for the design of Monoamine Oxidase (MAO) inhibitors. This study attempted to discover potent and selective chalcone-derived MAO inhibitors by synthesising a series consisting of various cyclic chalcone derivatives. The cyclic chalcones were selected based on the possibility that their restricted structures would confer a higher degree of MAO isoform selectivity, and included the following chemical classes: 1-indanone, 1- tetralone, 1-benzosuberone, chromone, thiochromone, 4-chromanone and 4-thiochromanone. The cyclic chalcone derivatives were synthesised via a one-pot Claisen-Schmidt condensation reaction. The MAO inhibitory properties of the chalcone derivatives were evaluated with the recombinant human MAO-A and MAO-B enzymes and the potencies were expressed as the IC50 values. A selected inhibitor was docked into an active site model of MAO-B. The results showed that the cyclic chalcones are in general good potency, and in most instances specific inhibitors of the MAO-B isoform. Among these compounds, the 4-chromanone derivative was the most potent MAO-B inhibitor with an IC50 value of 0.156 µM. To further investigate the MAO inhibition of cyclic chalcones, a series of twenty-three 2-benzylidene-1-tetralone derivatives were synthesised and evaluated as MAO inhibitors. Most 2-benzylidene-1-tetralones possess good inhibitory activity and specificity for MAO-B with the most potent inhibitor displaying an IC50 value of 0.0064 µM, while the most potent MAO-A inhibitor possessed an IC50 value of 0.754 µM. This study thus shows that certain cyclic chalcones are human MAO-B inhibitors, compounds that could be suitable for the treatment of neurodegenerative disorders such as Parkinson's disease.

Molecular Determinants of Substrate Specificity in Human Insulin-Degrading Enzyme.

Insulin-degrading enzyme (IDE) is a 110 kDa chambered zinc metalloendopeptidase that degrades insulin, amyloid β, and other intermediate-sized aggregation prone peptides that adopt β-structures. Structural studies of IDE in complex with multiple physiological substrates have suggested a role for hydrophobic and aromatic residues of the IDE active site in substrate binding and catalysis. Here, we examine functional requirements for conserved hydrophobic and aromatic IDE active site residues that are positioned within 4.5 Å of IDE-bound insulin B chain and amyloid β peptides in the reported crystal structures for the respective enzyme-substrate complexes. Charge, size, hydrophobicity, aromaticity, and other functional group requirements for substrate binding IDE active site residues were examined through mutational analysis of the recombinant human enzyme and enzyme kinetic studies conducted using native and fluorogenic derivatives of human insulin and amyloid β peptides. A functional requirement for IDE active site residues F115, A140, F141, Y150, W199, F202, F820, and Y831 was established, and specific contributions of residue charge, size, and hydrophobicity to substrate binding, specificity, and proteolysis were demonstrated. IDE mutant alleles that exhibited enhanced or diminished proteolytic activity toward insulin or amyloid β peptides and derivative substrates were identified.

Synthesis and Inhibitory Properties of Imines Containing Monoterpenoid and Adamantane Fragments Against DNA Repair Enzyme Tyrosyl-DNA Phosphodiesterase 1 (Tdp1)

Six imines including four new ones were synthesized via the reaction of monoterpenoid aldehydes with aminoadamantanes. The inhibitory activities of the synthesized compounds against purified human recombinant DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 (Tdp1) fell in the range IC50 = 5.5–7.1 μM.

PDn-3 DPA Pathway Regulates Human Monocyte Differentiation and Macrophage Function

SummaryMacrophages are central in orchestrating the clearance of apoptotic cells and cellular debris during inflammation, with the mechanism(s) regulating this process remaining of interest. Herein, we found that the n-3 docosapentaenoic acid-derived protectin (PDn-3 DPA) biosynthetic pathway regulated the differentiation of human monocytes, altering macrophage phenotype, efferocytosis, and bacterial phagocytosis. Using lipid mediator profiling, human primary cells and recombinant enzymes we found that human 15-lipoxygenases initiate the PDn-3 DPA pathway catalyzing the formation of an allylic epoxide. The complete stereochemistry of this epoxide was determined using stereocontrolled total organic synthesis as 16S,17S-epoxy-7Z,10Z,12E,14E,19Z-docosapentaenoic acid (16S,17S-ePDn-3 DPA). This intermediate was enzymatically converted by epoxide hydrolases to PD1n-3 DPA and PD2n-3 DPA, with epoxide hydrolase 2 converting 16S,17S-ePDn-3 DPA to PD2n-3 DPA in human monocytes. Taken together these results establish the PDn-3 DPA biosynthetic pathway in human monocytes and macrophages and its role in regulating macrophage resolution responses.

In vitro metabolism of desomorphine

Desomorphine is reported to be the principal pharmacologically active opioid in Krokodil, a homemade injectable drug that is perceived to be a cheaper alternative to heroin. There have been limited studies regarding its pharmacology or detection in biological matrices. The goal of this study was to contribute further knowledge regarding its metabolism. Recombinant human cytochrome P450 enzymes (rCYPs) and recombinant uridine 5′-diphospho-glucuronosyltransferases (rUGTs) were used to investigate the biotransformational pathways involved. Samples were analyzed by liquid chromatography/quadrupole-time of flight–mass spectrometry (LC–Q/TOF–MS). Seven rCYP (rCYP2B6, rCYP2C8, rCYP2C9, rCYP2C18, rCYP2C19, rCYP2D6 and rCYP3A4) enzymes were found to contribute to desomorphine metabolism and eight phase I metabolites were identified, including nordesomorphine, desomorphine-N-oxide, norhydroxydesomorphine, and five hydroxylated species. Inhibition assays were used to confirm individual rCYP isoenzyme activity. Nine rUGTs (rUGT1A1, rUGT1A3, rUGT1A8, rUGT1A9, rUGT1A10, rUGT2B4, rUGT2B7, rUGT2B15, and rUGT2B17) were found to contribute to the formation of desomorphine-glucuronide.

Carbonyl reduction of NNK by recombinant human lung enzymes: identification of HSD17β12 as the reductase important in (R)-NNAL formation in human lung.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most abundant and carcinogenic tobacco-specific nitrosamine in tobacco and tobacco smoke. The major metabolic pathway for NNK is carbonyl reduction to form the (R) and (S) enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) which, like NNK, is a potent lung carcinogen. The goal of this study was to characterize NNAL enantiomer formation in human lung and identify the enzymes responsible for this activity. While (S)-NNAL was the major enantiomer of NNAL formed in incubations with NNK in lung cytosolic fractions, (R)-NNAL comprised ~60 and ~95% of the total NNAL formed in lung whole cell lysates and microsomes, respectively. In studies examining the role of individual recombinant cytosolic reductase enzymes in lung NNAL enantiomer formation, AKR1C1, AKR1C2, AKR1C3, AKR1C4 and CBR1 all exhibited (S)-NNAL-formation activity. To identify the microsomal enzymes responsible for (R)-NNAL formation, 28 microsomal reductase enzymes were screened for expression by real-time PCR in normal human lung. HSD17β6, HSD17β12, KDSR, NSDHL, RDH10, RDH11 and SDR16C5 were all expressed at levels ≥HSD11β1, the only previously reported microsomal reductase enzyme with NNK-reducing activity, with HSD17β12 the most highly expressed. Of these lung-expressing enzymes, only HSD17β12 exhibited activity against NNK, forming primarily (>95%) (R)-NNAL, a pattern consistent with that observed in lung microsomes. siRNA knock-down of HSD17β12 resulted in significant decreases in (R)-NNAL-formation activity in HEK293 cells. These data suggest that both cytosolic and microsomal enzymes are active against NNK and that HSD17β12 is the major active microsomal reductase that contributes to (R)-NNAL formation in human lung.