One-carbon compounds such as methanol and methane are cheap and readily available feedstocks for biomanufacturing. Oxidation of methanol to formaldehyde catalyzed by methanol dehydrogenase (MDH) is a key step of microbial one-carbon metabolism. A variety of MDHs that depend on different co-factors and possess different enzymatic properties have been discovered from native methylotrophs. Nicotinamide adenine dinucleotide (NAD)-dependent MDHs are widely used in constructing synthetic methylotrophs, whereas this type of MDH usually suffers from low methanol oxidation activity and low affinity to methanol. Consequently, methanol oxidation is considered as a rate-limiting step of methanol metabolism in synthetic methylotrophs. To accelerate methanol oxidation, thereby improving the methanol utilization efficiency of synthetic methylotrophs, massive researches have focused on discovery and engineering of MDHs. In this review, we summarize the ongoing efforts to discover, characterize, and engineer various types of MDHs as well as the applications of MDHs in synthetic methylotrophs. Directed evolution of MDH and construction of multi-enzyme complexes are described in detail. In the future prospective part, we discuss the potential strategies of growth-coupled protein evolution and rational protein design for acquisition of superior MDHs.
Alcohol Oxidoreductases/genetics* ; Carbon ; Methane ; Methanol

The influence of different affinity tags on enzyme characteristics varies. The (S)-carbonyl reductase 2 (SCR2) from Candida parapsilosis can reduce 2-hydroxyacetophenone, which is a valuable prochiral ketones. Different affinity tags, i.e. his-tag, strep-tag and MBP-tag, were attached to the N terminus of SCR2. These tagged SCR2 enzymes, i.e. his6-SCR2, strep-SCR2 and MBP-SCR2, were heterologously expressed in Escherichia coli and purified to study their characteristics towards 2-hydroxyacetophenone reduction. Affinity tags did affect the characteristics of the recombinant SCR2 enzymes. Specifically, affinity tags affect the stability of recombinant SCR2 enzymes: 1) At pH 6.0, the remaining enzyme activities of his6-SCR2 and strep-SCR2 were only 95.2% and 90.0% of the untagged SCR2, while that of MBP-SCR2 was 1.2 times of the untagged SCR2 after incubating for 13 h at 30 °C. 2) The half-life of MBP-SCR2 at 50 °C was 26.6%-48.8% longer than those of strep-SCR2, his6-SCR2 and untagged SCR2. 3) The kcat of MBP-SCR2 was about 1.25-1.45 times of that of small affinity-tagged and untagged SCR2 after storing at -80 °C for 60 d. Structural informatics indicated that the α-helices at the C terminus of MBP-SCR2 contributed to the stability of the N terminus of fusion protein of SCR2. Data from circular dichroism showed that the MBP-tag has some influence on the secondary structure of SCR2, while melting temperature analysis demonstrated that the Tm of the recombinant MBP-SCR2 was about 5 °C higher than that of the untagged SCR2. This study obtained an efficient and stable recombinant SCR2, i.e. the MBP-SCR2. Moreover, this study could serve as a reference for other researchers to evaluate and select appropriate affinity tags for their research.
Alcohol Oxidoreductases ; Escherichia coli/genetics* ; Recombinant Fusion Proteins/genetics*

Mitochondrion-localized retinol dehydrogenase 13 (Rdh13) is a short-chain dehydrogenase/reductase involved in vitamin A metabolism in both humans and mice. We previously generated Rdh13 knockout mice and showed that Rdh13 deficiency causes severe acute retinal light damage. In this study, considering that Rdh13 is highly expressed in mouse liver, we further evaluated the potential effect of Rdh13 on liver injury induced by carbon tetrachloride (CCl). Although Rdh13 deficiency showed no significant effect on liver histology and physiological functions under regular culture, the Rdh13 mice displayed an attenuated response to CCl-induced liver injury. Their livers also exhibited less histological changes and contained lower levels of liver-related metabolism enzymes compared with the livers of wild-type (WT) mice. Furthermore, the Rdh13 mice had Rdh13 deficiency and thus their liver cells were protected from apoptosis, and the quantity of their proliferative cells became lower than that in WTafter CCl exposure. The ablation of Rdh13 gene decreased the expression levels of thyroid hormone-inducible nuclear protein 14 (Spot14) and cytochrome P450 (Cyp2e1) in the liver, especially after CCl treatment for 48 h. These data suggested that the alleviated liver damage induced by CCl in Rdh13 mice was caused by Cyp2e1 enzymes, which promoted reductive CCl metabolism by altering the status of thyroxine metabolism. This result further implicated Rdh13 as a potential drug target in preventing chemically induced liver injury.
Alcohol Oxidoreductases ; deficiency ; genetics ; Animals ; Carbon Tetrachloride Poisoning ; enzymology ; Chemical and Drug Induced Liver Injury ; enzymology ; pathology ; Cytochrome P-450 CYP2E1 ; metabolism ; Female ; Immunohistochemistry ; Liver ; drug effects ; enzymology ; pathology ; Male ; Mice ; Mice, 129 Strain ; Mice, Inbred C57BL ; Mice, Knockout ; Nuclear Proteins ; metabolism ; Transcription Factors ; metabolism

Objective To explore the change rules of blood ethanol and blood acetaldehyde concentration, the impairment of psychomotor functions of different acetaldehyde dehydrogenase （ALDH） 2 genotype individuals after alcohol consumption and the relationship among them. Methods The ALDH2 genotypes in seventy-nine healthy volunteers were obtained by SNaPshot^TM method, then divided into ALDH2*1/*1 （wild type） and ALDH2*1/*2 （mutant type） group. After volunteers consumed 1.0 g/kg of alcohol, blood ethanol concentration and blood acetaldehyde concentration at a series of time points before and after alcohol consumption and psychomotor functions, such as, visual selective response time, auditory simple response time and tracking experiment were detected. Biphasic alcohol response questionnaires were collected. Results After alcohol consumption, ALDH2*1/*2 group's blood ethanol and blood acetaldehyde concentration reached the peak earlier than ALDH2*1/*1 group. Its blood acetaldehyde concentration was higher than that of ALDH2*1/*1 group, 1-6 h after alcohol consumption. The psychomotor functions, such as visual selective response time and auditory simple response time in ALDH2*1/*2 group were more significantly impaired than those in ALDH2*1/*1 group after alcohol consumption. There was no statistical significance between the two groups in excitement or sedation reactions （P>0.05）. Pearson correlation coefficient test showed that blood acetaldehyde concentration was related with psychomotor function. Conclusion There are significant differences between the psychomotor function of ALDH2 wild type and mutant type individuals after alcohol consumption estimated to be related to the difference in blood acetaldehyde concentration after alcohol consumption.
Acetaldehyde/metabolism* ; Alcohol Drinking/blood* ; Aldehyde Dehydrogenase/genetics* ; Aldehyde Dehydrogenase, Mitochondrial ; Aldehyde Oxidoreductases ; Ethanol/metabolism* ; Genotype ; Humans ; Polymorphism, Genetic/genetics* ; Psychomotor Performance/physiology*

OBJECTIVETo explore pathogenic mutation in a family affected with 2-hydroxyglutaric aciduria.

METHODSExons of 3 candidate genes, including L2HGDH, D2HGDH and SLC25A1, were amplified with polymerase chain reaction and subjected to direct sequencing.

RESULTSDNA sequencing has found that the proband and his affected younger brother have both carried a heterozygous mutation c.845G>A (p.R282Q) in the exon 7 of the L2HGDH gene. The same mutation was not detected in the his sister who was healthy. Pedigree analysis has confirmed that the above mutation was inherited from the mother. No mutation was detected in exons and flanking sequences of the D2HGDH and SLC25A1 genes.

CONCLUSIONMutation of the L2HGDH gene probably underlies the 2-hydroxyglutaric aciduria in this family.

Alcohol Oxidoreductases ; genetics ; Base Sequence ; Brain ; diagnostic imaging ; Brain Diseases, Metabolic, Inborn ; diagnostic imaging ; enzymology ; genetics ; Child ; Female ; Humans ; Male ; Molecular Sequence Data ; Mutation ; Pedigree ; Radiography ; Young Adult

BACKGROUNDRetinoic acid (RA) is a potent signaling molecule that plays pleiotropic roles in patterning, morphogenesis, and organogenesis during embryonic development. The synthesis from retinol (vitamin A) to retinoic acid requires two sequential oxidative steps. The first step involves the oxidation of retinol to retinal through the action of retinol dehydrogenases. Retinol dehydrogenases1l (RDH1l) is a novel zebrafish retinol dehydrogenase. Herein we investigated the role of zebrafish RDH1l in heart development and cardiac performance in detail.

METHODSRDH1l specific morpholino was used to reduce the function of RDH1l in zebrafish. The gene expressions were observed by using whole mount in situ hybridization. Heart rates were observed and recorded under the microscope from 24 to 72 hours post fertilization (hpf). The cardiac performance was analyzed by measuring ventricular shortening fraction (VSF).

RESULTSThe knock-down of RDH1l led to abnormal neural crest cells migration and reduced numbers of neural crest cells in RDH1l morphant embryos. The reduced numbers of cardiac neural crest cells also can be seen in RDH1l morphant embryos. Furthermore, the morpholino-mediated knock-down of RDH1l resulted in the abnormal heart loop. The left-right determining genes expression pattern was altered in RDH1l morphant embryos. The impaired cardiac performance was observed in RDH1l morphant embryos. Taken together, these data demonstrate that RDH1l is essential for the heart development and cardiac performance in zebrafish.

CONCLUSIONSRDH1l plays a important role in the neural crest cells development, and then ultimately affects the heart loop and cardiac performance. These results show for the first time that an enzyme involved in the retinol to retinaldehyde conversion participate in the heart development and cardiac performance in zebrafish.

Alcohol Oxidoreductases ; genetics ; metabolism ; Animals ; Animals, Genetically Modified ; Heart ; embryology ; Zebrafish ; Zebrafish Proteins ; genetics ; metabolism

Bacillus sp. TSH1 is a butanol-producing microorganism newly isolated in our laboratory; it can grow and ferment under facultative anaerobic conditions, while sharing similar fermentation pathways and products with Clostridium acetobutylicum. To illustrate the relationships between the products and the enzyme activities in Bacillus sp. TSH1, key butanol- and ethanol-forming enzymes were studied, including butyraldehyde dehydrogenase, butanol dehydrogenase and alcohol dehydrogenase. The activities of the three enzymes increased rapidly after the initiation of fermentation. Activities of three enzymes peaked before 21 h, and simultaneously, product concentrations also began to increase gradually. The maximum activity of alcohol dehydrogenase was 0.054 U/mg at 12 h, butyraldehyde dehydrogenase 0.035 U/mg at 21 h and butanol dehydrogenase 0.055 U/mg at 15 h. The enzyme activities then decreased, but remained constant at a low level after 24 h, while the concentrations of butanol, acetone, and ethanol continued increasing until the end of the fermentation. The results will attribute to the understanding of the butanol metabolic mechanism, and provide a reference for further study of a facultative Bacillus metabolic pathway.
Alcohol Dehydrogenase ; metabolism ; Alcohol Oxidoreductases ; metabolism ; Aldehyde Oxidoreductases ; metabolism ; Anaerobiosis ; Bacillus ; classification ; genetics ; metabolism ; Butanols ; metabolism ; Fermentation ; Metabolic Networks and Pathways

Carbonyl reductases catalyze carbonyl compounds to chiral alcohols that are important building blocks in fine chemical industry. To study carbonyl reductase from Pichia pastoris GS115 (ppcr), we discovered a new gene (ppcr) encoding an NADPH-dependent carbonyl reductase by genomic data mining. It was amplified by PCR from the genomic DNA, and expressed in Escherichia coli BL21 (DE3). The recombinant protein was purified to homogeneity. The optimum temperature was 37 degrees C and the optimum pH of PPCR was 6.0. PPCR was stable below 45 degrees C. The Km and k(cat) value of the enzyme for ethyl 3-methyl-2-oxobutanoate were 9.48 mmol/L and 0.12 s, respectively. The enzyme had broad substrate specificity and high enantioselectivity. It catalyzed the reduction of aldehydes, a-ketoesters, beta-ketoesters and aryl ketones to give the corresponding alcohols with >97% ee with only a few exceptions, showing its application potential in the synthesis of chiral alcohols.
Alcohol Oxidoreductases ; biosynthesis ; chemistry ; genetics ; Amino Acid Sequence ; Biotechnology ; methods ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Molecular Sequence Data ; Pichia ; enzymology ; Recombinant Proteins ; biosynthesis ; chemistry ; genetics ; Stereoisomerism ; Substrate Specificity ; Temperature

Asymmetric reduction of bulky diaryl ketones is still one of the challenging tasks in biocatalysis. By genomic data mining, a putative carbonyl reductase gene pascr was found in Pichia pastoris GS115. pascr was cloned and over-expressed in Escherichia coli Rosseta2 (DE3). The recombinant enzyme was purified to homogeneity by Ni-NTA column and its catalytic properties were studied. PasCR strictly used NADPH as cofactor, gel filtration and SDS-PAGE analysis suggested that the native form of PasCR was a dimmer. PasCR exhibited the highest activity at 35 degrees C in phosphate buffer at pH 6.5. The enzyme catalyzed the reduction of some bulky diaryl ketones, such as 4-methylbenzophenone, 2-methylbenzophenone and 4-chlorobenzophenone, especially for 4-methylbenzophenone, the product S--alcohol was obtained with 85% ee.
Alcohol Oxidoreductases ; genetics ; Amino Acid Sequence ; Catalysis ; Cloning, Molecular ; Ketones ; chemistry ; Molecular Sequence Data ; Pichia ; enzymology ; genetics ; Stereoisomerism

The gene expressions of codeinone reductase (COR) and berberine bridge enzyme (BBE) in Papaver somniferum were blocked by RNA hairpin of RNA interference (RNAi). The complete sequences of COR and BBE genes were cloned by reverse transcription-polymerase chain reaction (RT-PCR), the results of homology comparison revealed that the cloned COR and BBE genes had high homology with the other gene family members reported in the GenBank. The target sequences of COR and BBE genes were screened in accordance with the design principle of RNAi, a 643 bp fusion gene was obtained by the method of overlapping PCR, then plant expression vector ihpRNA was constructed based on intermediate vector pHANNIBAL and plant expression vector pCEPSPS. With that 78 transgenic plants were obtained through Agrobacterium-mediated and 17 positive plants were screened by PCR, that could initially indicate that the target fragments of COR and BBE gene had been integrated into tobacco genome.
Artificial Gene Fusion ; Genetic Vectors ; NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases ; genetics ; Oxidoreductases, N-Demethylating ; genetics ; Papaver ; enzymology ; genetics ; Plants, Genetically Modified ; enzymology ; genetics ; RNA Interference ; RNA, Small Interfering ; Tobacco ; genetics ; Transformation, Genetic