Succinic semialdehyde dehydrogenase deficiency (SSADHD), caused by variants in ALDH5A1, is a rare inherited neurometabolic disorder with phenotypic heterogeneity. To clarify the pathogenicity of ALDH5A1 variants, we systematically investigated their effects on succinic semialdehyde dehydrogenase (SSADH) structure and function. We obtained the clinical and molecular characteristics of 12 probands. We further augmented the pathogenicity dataset for 14 variants using multiple in silico tools under the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guideline. More importantly, we provided quantitative data on protein expression and residual enzyme activity for SSADH, enabling robust assignment of ACMG PS3/BS3 codes. Finally, we integrated 3D structural modelling with changes in physicochemical properties to butter elucidate how individual variants impair SSADH function. Patients with SSADHD exhibit varying degrees of epilepsy, intellectual disorders, developmental delay, and hypotonia. Among the 14 variants, 9 affect SSADH expression level of protein, and 9 affect SSADH enzyme activity. After acquiring functional experiments' results, PS3 was assigned to 10 variants and BS3 to 1; more notably, 8 variants obtained more plentiful pathogenic evidence. Intriguingly, we also investigated the underlying mechanisms using protein-based prediction techniques, 2 of 14 variants influenced binding of SSADH to small molecules, whereas 3 of 14 variants led to instability. Besides, as the SSADH with variants in the oligomerization domain accumulates in the tetramer, the tetramer becomes increasingly unstable. In this study, we illustrated that 14 ALDH5A1 variants affected the molecular structure and function by diverse mechanisms, and with varying degrees, which could help us to gain a deeper understanding of these variants by providing reasonable evidence based on the PS3/BS3 codes in the ACMG guidelines. Essentially, this pathogenic classification facilitates the diagnosis of SSADHD in future genetic testing processes.

Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare autosomal recessive metabolic disorder due to loss-of-function ALDH5A1 mutations impairing the catabolism of γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the brain. In SSADHD, pathologic accumulation of GABA and its metabolic by-product γ-hydroxybutyrate (GHB) corresponds to a clinical syndrome dominated by developmental delay and epilepsy in half of patients with risk of sudden death in adolescence and adulthood. Brain-wide ALDH5A1 gene replacement for SSADHD is unavailable, and whether such treatment will reverse the SSADHD phenotype is unknown. We developed an inducible mouse SSADHD model, Aldh5a1 lox-STOP , enabling Cre-dependent Aldh5a1 restoration to evaluate gene therapy feasibility. In the absence of SSADH, Aldh5a1 lox-STOP mice exhibit hyperactivity and excessive serum GHB levels, culminating in death by ∼postnatal day 22, recapitulating the severe SSADHD condition. Systemic delivery of a blood-brain barrier (BBB)-penetrating adeno-associated virus (AAV) carrying a Cre gene to Aldh5a1 lox-STOP mice leads to brain-wide SSADH restoration, serum GHB level reduction, normalization of hyperactivity, and substantial increase in survival. As a step toward clinical translation, we further assessed an AAV encompassing a functional native promoter (FLnP) of ALDH5A1 tethered to its human coding sequence, namely AAV-FLnP-hALDH5A1. Aldh5a1 lox-STOP mice were effectively rescued when treated with AAV-FLnP-hALDH5A1 packaged in the blood-brain barrier (BBB)-penetrating capsid PHP.eB. These findings provide preclinical proof that SSADH gene replacement therapy is feasible and potentially effective.

ABSTRACTSuccinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessive neurometabolic disorder caused by biallelic pathogenic variants in ALDH5A1, encoding the mitochondrial enzyme SSADH. This enzyme catalyses the conversion of succinic semialdehyde to succinic acid in the γ‐aminobutyric acid (GABA) degradation pathway. SSADH deficiency leads to the accumulation of neurotoxic metabolites, including γ‐hydroxybutyrate (GHB), and presents with developmental delay, hypotonia, ataxia, seizures, behavioral disturbances, and intellectual disability. We report a 10‐month‐old Caucasian male with global developmental delay, central hypotonia, and delayed motor milestones. He presented acutely with left‐sided hemiplegia following irritability and vomiting. Brain MRI showed bilateral (right > left) T2 hyperintensities and diffusion restriction in the globus pallidus. Urine organic acid analysis via gas chromatography–mass spectrometry revealed markedly elevated 4‐hydroxybutyric acid and 4,5‐dihydroxyhexanoic lactone, pathognomonic for SSADH deficiency. Molecular testing identified compound heterozygous ALDH5A1 variants: c.278G>T p.(Cys93Phe) and c.612G>A p.(Trp204*), both previously reported as pathogenic. Parental segregation confirmed trans configuration. Three weeks postillness, he developed focal seizures, which have remained well controlled on levetiracetam. His seizure onset in infancy is notably earlier than the typical early childhood onset (~9 years) reported in SSADH deficiency. This case expands the phenotypic spectrum of SSADH deficiency to include metabolic stroke as a presenting feature in infancy and highlights the importance of early recognition and molecular confirmation to guide management and emerging therapeutic strategies.

While the role of succinic semialdehyde (SSA) dehydrogenase (SSADH; also known as gabD) is well-reported from model plants, the lack of functionality and structure of SSADH from citrus represents a significant knowledge gap. Herein, genome-wide analyses identified 17 high-confidence SSADH-like proteins from Citrus sinensis, among which three putative SSADHs have potential GABA dehydrogenase function. Sequence alignment, phylogenetic analyses, and domain architecture demonstrated high conservation among CsSSADHs (aka CsgabD) and their homologs across diverse plant taxa. Notably, CsSSADH-2 lacked a conserved QGIVC motif found in CsSSADH-1/-3. Secondary structure analyses indicated conserved aldehyde dehydrogenase domains. Homology-based 3D modeling predicted CsSSADH-1 and 2 as homo-tetramers; however, AlphaFold2-based modeling suggested their full-length monomer structures. PPI networks revealed CsSSADH-1 interacts with 10 proteins, primarily involved in GABA/succinate metabolism and the TCA cycle. Docking studies indicated that CsSSADH-1 displayed acceptable affinity and binding modes with GABA, SSA, and succinate. GABA supplementation enhances CsSSADH expression, GABA, and succinate content in a dose-dependent manner in both healthy and infected citrus plants under greenhouse conditions. CsSSADH was involved in citrus responses to 'Candidatus Liberibacter asiaticus' and/or its vector, Diaphorina citri. Nevertheless, GABA accumulation under biotic stress leads to condition-specific rerouting of GABA metabolism. Chemical inhibition of CsSSADH resulted in increased GABA accumulation but reduced succinate levels in both healthy and infected plants. This study offers the first comprehensive characterization of C. sinensis SSADH isoforms, providing insights into their evolutionary divergence, structural features, and potential functions, and enhancing our understanding of their possible roles in GABA metabolism and citrus defense responses.

BackgroundHydrocarbon-based biofuels, known as drop-in fuels, which are chemically similar to petroleum, have gained significant attention. Microorganisms that produce medium-chain alkanes hold promise for the bioproduction of drop-in fuels. Previous studies identified Klebsiella sp. NBRC100048 as having aldehyde-decarbonylating activity, enabling it to convert aldehydes into alkanes. Using a genomic fosmid library from Klebsiella sp. NBRC100048, we identified open reading frame 2991 (orf2991), which catalyzes the conversion of tetradecanal to tridecane. This gene shares high sequence similarity with the aldehyde dehydrogenase (ALDH) family in Escherichia coli.ResultsALDH homolog genes from Klebsiella sp. NBRC100048 and E. coli W3110 were cloned and expressed in E. coli to assess their potential alkane-synthesizing activity. Approximately one-fifth of the tested enzymes exhibited this function, with basic local alignment search tool (BLAST) analysis classifying them under the phenylacetaldehyde dehydrogenase, succinate-semialdehyde dehydrogenase, or aldehyde dehydrogenase B families. Testing additional ALDH homologs from diverse organisms—bacteria, fungi, plants, and animals—revealed that ALDHs with alkane-synthesizing activity are widespread, occurring in Gram-positive bacteria, actinomycetes, lactic acid bacteria, and yeast species. Alkane-synthesizing activity was observed with resting cells and cell-free extracts of the E. coli transformants expressing ALDH (ORF2991) from Klebsiella sp. NBRC100048 with aldehyde as the substrate in the presence of NADH. However, under the tested conditions, the purified enzyme alone did not show detectable decarbonylase activity. These results suggest that additional cellular components, cofactors, or specific conditions may be required for the purified enzyme to exhibit the activity.ConclusionsWe cloned several aldehyde dehydrogenases (ALDHs) from bacteria and yeast that have aldehyde decarbonylase activity to convert aldehydes to alkanes. Alkane-synthesizing activity was observed through the assays using resting cells and cell-free extracts of the E. coli transformants expressing ALDH. This novel function of aldehyde dehydrogenase introduces a new pathway for hydrocarbon fuel production and offers novel insights into microbial processes that may explain the natural origins of petroleum.

Encapsulated GABA coatings as a postharvest strategy to enhance mango chilling tolerance.

Abstract — Using directly engineered derivatives of previously constructed succinate-producing Escherichia coli strain SUC1.0 (pMW119- kgd ) (MG1655 ∆ ackA-pta , ∆ poxB , ∆ ldhA , ∆ adhE , ∆ ptsG , P L glk , P tac galP , ∆ aceBAK , ∆ glcB , ∆ sdhAB , pMW119- kgd ) the feasibility of gamma-aminobutyric acid biosynthesis from glucose by this bacterium resulting from a partial reversal of GABA-shunt was demonstrated. The formation of succinate semialdehyde from 2-ketoglutarate was ensured in the strain resulting from the expression of Mycobacterium tuberculosis 2-ketoglutarate decarboxylase gene. Conversion of succinate semialdehyde to succinic acid was prevented by the inactivation of cellular NAD + - and NADPH + -dependent succinate semialdehyde dehydrogenases. Formation of the target substance by the action of native 4-aminobutyrate aminotransferase was achieved upon the inactivation of glutamate decarboxylases A and B. Enhancement of 4-aminobutyrate aminotransferase gene expression led to an increase in the molar yield of gamma-aminobutyric acid from glucose demonstrated by the strain synthesizing the target product through the partially reversed GABA-shunt from ~11 to ~25%.

The halotolerant endophytic bacterial Pseudomonas strain EB3 isolated from the roots of the mangrove plant species Avicennia alba, has been reported to promote plant growth and mitigate the adverse effects of salt stress. However, the genetic mechanisms of the strain that may explain these processes are unknown. This study aimed to determine the whole genome sequence of EB3 and conduct expression analysis of EB3 genes putatively involved in salt tolerance and plant growth promotion. EB3-inoculated banana (Musa acuminata cv. Berangan) plantlets were subjected to 100mM sea salt. These inoculated plants exhibited significantly improved growth compared to non-inoculated controls under the same salinity stress. Whole-genome sequencing of EB3 revealed a genome size of 6 006 826bp. Phylogenetic analysis based on whole-genome comparison indicated that EB3 is closely related to Pseudomonas juntendi. Functional annotation of the genome identified a large number of genes associated with key biological processes, including stress resistance, iron uptake system, plant root colonization, and plant growth promotion. The increased expression of succinate-semialdehyde dehydrogenase (gabD), pyrroloquinoline quinone biosynthesis proteins (pqqBDEF), acetylglutamate kinase (argB), NADP-specific glutamate dehydrogenase (gdhA), N-acetylglutaminylglutamine synthetase (ngg), and superoxide dismutase family protein (sodC) genes in EB3, when EB3-inoculated plants were placed under salt stress, further supported their potential involvement in salt tolerance and growth-promoting activities. Together, the genomic insights and gene expression data confirm the functional potential of the EB3 strain as a plant growth-promoting bacterium (PGPB) even under saline conditions.

A metabolic pathway for degrading 4-hydroxyphenylacetate (4-HPA) is crucial for environmental and pathogenic microbes to assimilate aromatic compounds. The 4-HPA degradation pathway in Acinetobacter baumannii TH comprises multiple reactions that are not fully understood. Enzymes involved in the first two steps (a two-component 4-HPA-3-hydroxylase, and 3,4-dihydroxyphenylacetate 2,3-dioxygenase) and the last two steps (4-hydroxy-2-keto-heptane-1,7-dioate aldolase and succinic semialdehyde (SSA) dehydrogenase (SSADH)) have been identified and studied, while the enzymes functioning in the middle of the pathway remain uncharacterized. Here, we identified products associated with individual enzymes including 5-carboxymethyl-2-hydroxymuconate-semialdehyde (CHMS) dehydrogenase (CHMSD), 5-carboxymethyl-2-hydroxymuconate (CHM) isomerase (CHMI), five-oxo-pent-3-ene-1,2,5-tricarboxylate (OPET) decarboxylase (OPETD), 2-hydroxy-hept-2,4-diene-1,7-dioate (HHDD) isomerase (HHDDI) and two-oxo-hept-3-ene-1,7-dioate (OHED) hydratase (OHEDH). We used enzymatically synthesized OPET (a tri-acid) to probe the decarboxylation step and found that the highest decarboxylation efficiency was achieved when OPETD, CHMI, and HHDDI were all present in the reaction. We demonstrated that CHMI was responsible for tri-acid tautomerization, while the protein-protein interactions between OPETD and HHDDI enhanced the decarboxylation by OPETD to generate OHED (a di-acid). OHEDH is distinct from other hydratases in that it requires Mn2+ as a cofactor. Notably, besides CHMS, CHMSD can use SSA, a substrate of SSADH, suggesting that CHMSD can substitute for SSADH to generate succinate for cellular utilization. Our studies herein completely assigned the catalytic functions of all enzymes in the 4-HPA degradation pathway. The knowledge gained will be valuable for developing inhibitors targeting enzymes unique to pathogenic microbes or for constructing cascade reactions to convert lignin-derived compounds into valuable biochemicals.

Background/Objectives: γ-aminobutyric acid (GABA), a non-protein amino, is synthesized from glutamic acid through the catalytic activity of glutamate decarboxylase (GAD). As a key signaling molecule, GABA plays a vital role in plant responses to abiotic stresses. To explore the potential involvement of the GABA gene family in Juglans regia’s response to environmental stressors, a comprehensive genome-wide identification and analysis of GABA-related genes was performed. Methods: The study examined their protein features, evolutionary relationships, chromosomal locations, and promoter cis-regulatory elements. Additionally, the expression patterns of GABA family genes were analyzed in J. regia seedlings subjected to salt and drought stress. Results: Genome analysis identified three main components of the GABA metabolic pathway in J. regia: glutamate decarboxylases (GADs), GABA transaminases (GABA-Ts), and succinic semialdehyde dehydrogenases (SSADHs). These genes were unevenly distributed across 14 chromosomes, with chromosome 10 containing the highest number. Promoter analysis revealed that about 80% of cis-acting elements were linked to plant hormone regulation, such as abscisic acid (ABA), and stress responses, including drought and high-salinity. Phylogenetic analysis showed that JrGAD1 was distantly related to other JrGAD members, while certain JrGABA-T and JrSSADH genes formed closely related pairs. Under salt and drought stress, JrSSADH23 expression was highly upregulated (2.60-fold and 2.24-fold, respectively), a trend observed for most JrSSADH genes. Conclusions: These findings offer valuable insights into the molecular basis of GABA metabolism in J. regia’s stress adaptation and identify promising genetic targets for developing stress-tolerant varieties.

Cognitive dysfunction is a core feature of schizophrenia (SCZ), yet its mechanisms remain poorly understood. We investigated the functional role of NKAPL (nuclear factor κB activating protein-like)-an SCZ risk-associated gene-and the single nucleotide polymorphism rs1635 in cognitive deficits related to SCZ. We used Nkapl transgenic mouse models to explore the impact of NKAPL on SCZ-related cognitive deficits. NKAPL acts as a transcriptional repressor of the γ-aminobutyric acid (GABA) metabolizing enzyme succinic semialdehyde dehydrogenase (SSADH). Nkapl deletion in medial prefrontal cortex (mPFC) interneurons led to increased SSADH levels, reduced GABA concentration in the synaptic cleft, impaired inhibitory synaptic transmission, and cognitive deficits. Furthermore, the rs1635 mutation (T153N) caused similar effects as the Nkapl knockout. Reexpression of wild-type NKAPL or genetic knockdown of SSADH in mPFC interneurons restored the synaptic dysfunction and cognitive deficits in Nkapl-/- mice. Our study indicates the potential role of NKAPL and SSADH in mPFC interneurons in neuronal mechanisms of learning and memory in mice.

The nitrogen regulator AreA modulates lipid metabolism through uga2 in Mucor circinelloides.

Treatable and preventable causes of inborn errors of metabolism: Cohort of neurotransmitter disorders in children from India.

Severe epilepsy phenotypes in adults with succinic semialdehyde dehydrogenase deficiency: Novel clinical and therapeutic insights from an Italian multicenter retrospective cohort study.

A significant challenge of mRNA-based protein replacement therapies is the diminishing efficacy and escalating toxicity associated with repeated dosing of lipid nanoparticles (LNPs). Many existing lipid formulations were originally designed for vaccine and are not optimized for therapeutic applications. We developed two libraries of ionizable lipids—one based on piperazine and the other on a newly introduced cyclohexane structure—with variations in linker and tail groups to enhance molecular diversity. GC Biopharma’s cyclohexane- and piperazine-based LNPs (GCP LNPs) supported stable and high-level expression without inducing liver toxicity under repeated dosing regimens. These LNPs effectively corrected disease markers in mouse models of phenylketonuria (PKU) and succinic semialdehyde dehydrogenase (SSADH) deficiency. Specially, we observed that the rigid structure and chemical stability of cyclohexane-based lipids contributed to sustained delivery performance. These findings offer a promising direction for the development of LNPs suitable for chronic mRNA-based therapies.

BackgroundThe pyrroline-5-carboxylate synthetase (P5CS), succinic semialdehyde dehydrogenase (SSADH), and dehydrin (DHN) genes are involved in plant drought response.MethodsA comprehensive bioinformatics approach was applied, including phylogenetic, structural, evolutionary, and functional analyses, as well as promoter, subcellular localization, and gene ontology assessments.ResultsThis is the first study to identify the P5CS, SSADH and DHN genes in Solanum lycopersicum via genome-wide analysis under drought stress. We identify 2 P5CS, 18 SSADH and 16 DHN genes in S. lycopersicum. The chromosomal distribution showed that P5CS genes were located on chromosomes 6 and 8, SSADH genes on chromosomes 1, 2, 3, 5, 6, 7, 8, 9, and 12, and DHN genes on chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 9,10, and 12. The Ka/Ks ratios indicated that the P5CS, SSADH and DHN genes were influenced primarily by negative selection, which indicated that the P5CS, SSADH and DHN genes received strong environmental pressure during evolution.The duplication time of the P5CS paralogous gene pairs was approximately 40.030 Mya. The duplication time of the SSADH paralogous gene pair ranged from approximately 31.495 to 45.966 Mya. The duplication time of the DHN paralogous gene pairs ranged from approximately 1.645 to 102.128 Mya. Synteny analysis of the P5CS, SSADH and DHN genes revealed collinearity orthologous relationships in Solanum tuberosum and Arabidopsis thaliana but no orthologs of the P5CS, SSADH and DHN genes with Oryza sativa. In addition, collinearity analysis revealed that 1 orthologous P5CS genes, 20 orthologous SSADH genes and 5 orthologous DHN genes were paired with those in S. tuberosum. Additionally, collinearity analysis revealed that 15 orthologous SSADH genes, 5 orthologous DHN gene and no orthologous P5CS genes, were paired with those in A. thaliana. The qRT–PCR results indicated that P5CS and DHN were upregulated, with fold changes of 2.39 and 1.23, respectively, whereas SSADH expression decreased with a fold change of 0.73.ConclusionsOur results provide comprehensive insights into the P5CS, SSADH, and DHN genes, including their protein structures and predicted interaction features. These findings offer valuable targets for tomato breeding programs aimed at developing stress-tolerant varieties under changing climate conditions.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07057-w.

Sheath blight (ShB) disease, caused by Rhizoctonia solani Kuhn, poses a significant economic threat to rice production world wide. Acknowledging the limited understanding of ShB resistance proteomics in highly resistant germplasm, our study aimed to unravel the proteomic intricacies underlying the interaction between resistant landrace Nizam Shait and R. solani. Utilizing Nizam Shait and BPT-5204 as representatives of ShB resistance and susceptibility, a comparative proteome analysis was performed using Orbitrap-Fusion mass spectrometry. The analysis unveiled 5133 differentially expressed proteins, with 118 significantly upregulated and 172 significantly downregulated at 0.05 p-value. Functional annotation revealed that the proteins associated with jasmonic acid-induced systemic resistance (JA-ISR), brassinosteroid (BR) signaling pathway, terpenoid biosynthesis, cell wall remodeling and carbohydrate metabolism showed significant upregulation in Nizam Shait upon ShB infection. The proteins associated with systemic acquired resistance (SAR), pathogenesis related proteins, cell redox homeostasis and cell death were downregulated, Notably, the 14-3-3 like protein GF-E exhibited highest upregulation, indicating its pivotal role in defense modulation through the brassinosteroid signaling pathway. The two key proteins of gamma-aminobutyric acid (GABA) shunt mediated defense, Succinate-semialdehyde dehydrogenase and Gamma-aminobutyrate transaminase were upregulated in Nizam Shait versus BPT-5204 and many other defense proteins were upregulated. Key signaling pathways involved in ShB resistance in Nizam Shait encompassed PTI via JA-ISR, cell wall strengthening, and brassinosteroid mediated resistance. Validation of the proteome data through RT-qPCR corroborated the findings, highlighting the significance of this research for future proteome assisted breeding efforts aimed at developing ShB resistant rice varieties.In conclusion, the current study deciphers pathways responsible for high resistance in landrace Nizam Shait against R. solani and identifies key proteins in Rice-R. solani interaction.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-85918-y.

γ-aminobutyrate (GABA) is a non-proteinogenic amino acid produced by glutamate decarboxylase (GAD) that functions as a vital neurotransmitter in animals, and as an important metabolite and signaling molecule in plants and microbes. “GABase” consists of a mixture of recombinant GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSDH) that is widely used for spectrophotometric quantification of glutamate decarboxylase (GAD) activity or GABA levels in tissue extracts. Both can be conveniently monitored at 340 nm owing to the sequential conversion of GABA into succinate by GABA-T and SSDH, and concomitant reduction of NADP+ into NADPH by SSDH. Currently, these assays rely on commercially available GABase from Pseudomonas fluorescens. However, the excessive cost of commercial GABase prompted us to develop an inexpensive and rapid “DIY” method for producing GABase by cloning, expressing and purifying His6-tagged GABA-T and SSDH from Escherichia coli. We validated our in-house GABase preparation by comparing GAD activities and GABA levels of the model plant Arabidopsis thaliana with those obtained using commercial GABase. Both pET30a plasmids for expressing E. coli His6-GABA-T and His6-SSDH have been deposited into AddGene (www.addgene.com). Our protocols for producing and using recombinant E. coli GABase should be of interest to any researcher who studies eukaryotic or prokaryotic GABA and/or GAD activity.

The fermentative production of the functional precursor 2,4-dihydroxybutyrate (DHB) enables sustainable synthesis of the methionine analogue hydroxy-4-(methylthio) butyrate, which is currently still produced from fossil fuels. In this work, we aimed to optimize the aerobic production of DHB from glucose through the synthetic malyl phosphate (MalP) pathway, which comprises the conversion of the natural TCA cycle intermediate malate into MalP and the subsequent reactions to yield malate semialdehyde (MalSA) and finally DHB. We first implemented the synthetic pathway in an engineered Escherichia coli strain previously reported to over-produce malate through the oxidative TCA cycle. However, DHB was only detected in trace amounts, while acetate and malate were secreted in high quantities. Subsequent construction of strains producing malate, but negligible amounts of acetate, revealed that an increased supply of malate alone is not sufficient for improved production of DHB. Instead, we discovered metabolic inefficiencies in the DHB pathway as we found that deleting the endogenous succinate semialdehyde dehydrogenase Sad, whose natural substrate is structurally similar to MalSA, strongly improved performance of the DHB pathway. Specifically, with the single knock-out of sad we could achieve a 3-fold increase in DHB production with a yield of 0.15molmol-1 compared to the wildtype host in shake flask experiments. With additional chromosomal expression of the mutant ppc K620S gene encoding the malate-insensitive phosphoenolpyruvate carboxylase under control of a weak constitutive promoter, we achieved a DHB yield of 0.22molmol-1, which corresponds to 17% of the maximal yield under aerobic conditions.

Update on inherited disorders of GABA metabolism.