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*

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

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

Alcohol Oxidoreductases ; genetics ; isolation & purification ; Cloning, Molecular ; Hep G2 Cells ; Humans ; Two-Hybrid System Techniques

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

OBJECTIVETo assess the efficacy of denaturing high-performance liquid chromatography (DHPLC) as a new screening assay for sequence variation in SNP detecting and new approach to SNP genotyping.

METHODSDHPLC was used to screen SNPs in 8 DNA pools each consisting of DNA from 5 individuals, and genotype the identified SNPs in 150 Chinese subjects from Hong Kong.

RESULTSSeventeen SNPs were identified: 12 were novel and 5 were previously reported; 11 were found in screening stage and the other 6 were found in genotyping stage; 2 were only found in Caucasian samples; 3 showed ethnic difference of minor allele frequency(MAF); 7 were common with the MAF>0.05 in Chinese samples.

CONCLUSIONThe results demonstrated the efficiency of DHPLC in screening SNPs when coupled with DNA pooling strategy, and in genotyping SNPs.

Alcohol Oxidoreductases ; genetics ; Chromatography, High Pressure Liquid ; methods ; Genotype ; Humans ; Point Mutation ; Polymorphism, Single Nucleotide ; genetics ; Sequence Analysis, DNA

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

OBJECTIVETo explore the relationship between genetic polymorphisms of the ethanol metabolizing enzymes and the occurrence of alcoholic liver disease (ALD).

METHODSSixty-five healthy male controls and 165 alcoholisms (including 122 ALD patients and 43 male alcohol abusers without liver complications defined as alcohol-dependent) were analyzed by polymerase chain reaction and hybridized with oligonucleotide microarray to detect the polymorphisms of the ethanol metabolizing enzymes genes.

RESULTSThe frequencies of alcohol dehydrogenase gene 2 * 1 ( ADH2 * 1 ) allele were shown as 37.69%, 46.51% and 59.02% in control, alcohol-dependent and ALD groups respectively; while those of ADH2 * 2 allele were shown as 62.31 %, 53.49% and 40.98% respectively. No ADH2 * 3 was detected in any of the subjects. The frequency of ADH2 * 1 was significantly higher in alcoholisms (ALD group and alcohol-dependent group) than in healthy controls ( P < 0. 01), and significantly higher in ALD group than in alcohol-dependent group ( P < 0.05) . The frequency of ADH3 * 2 was significantly higher in alcohol-dependents than in healthy controls ( P < 0.05) . The frequencies of ALDH2 * 2 allele mutation were significantly lower in alcoholisms than that in the healthy controls, and the deference between ALD group and alcohol-dependent group was significant. No homozygotes for the mutant ALDH2 * 2 allele were found in either alcoholic groups.

CONCLUSIONSPolymorphic ADH2, ADH3 and ALDH2 genes can affect the propensity for alcohol drinking in Chinese. The alleles of ADH2 * 2, ADH3 * 1 and ALDH2 * 2 are most likely to play a protective role against excessive consumption. ADH2 * 2 and ALDH2 X 2 may contribute to susceptibility for ALD.

Alcohol Dehydrogenase ; genetics ; Aldehyde Oxidoreductases ; genetics ; Genotype ; Humans ; Isoenzymes ; genetics ; Liver Diseases, Alcoholic ; genetics ; Male ; Oligonucleotide Array Sequence Analysis ; Polymorphism, Genetic

The 1,3-propanediol oxidoreductase isoenzyme encoding gene (yqhD) from E. coli was amplified by PCR. yqhD was inserted in pEtac to yield the recombinant expression vector pEtac-yqhD. Over-expression of yqhD in E. coli JM109 was achieved with pEtac-yqhD. SDS-PAGE analysis showed an over-expressed recombinant product at about 43 kD, consistent with the molecular weight predicted from gene sequence. Compared with E. coli JM109 (pEtac), the 1,3-propanediol oxidoreductase isoenzyme activity of the recombinant E. coli (pEtac-yqhD) reached 120 u/mg protein under the induction of 1.0 mmol/L IPTG at 37 degrees C for 4 hours; at similar conditions, enzyme activity of E. coli JM109 (pEtac) was only 0.5 u/mg protein. The recombinant E. coli JM109 (pUCtac-dhaB, pEtac-yqhD) was constructed. After induction with 1.0 mmol/L IPTG, the recombinant strain could transform 50 g/L glycerol to 38 g/L 1,3-propanediol under aerobic conditions. This work demonstrated firstly that the 1,3-propanediol oxidoreductase isoenzyme could show high activity under aerobic conditions.
Aerobiosis ; Alcohol Dehydrogenase ; Alcohol Oxidoreductases ; genetics ; metabolism ; Aldehyde Reductase ; genetics ; metabolism ; Escherichia coli ; enzymology ; genetics ; Escherichia coli Proteins ; genetics ; metabolism ; Genetic Engineering ; methods ; Isoenzymes ; Propylene Glycols ; metabolism ; Recombinant Proteins ; genetics ; metabolism