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A wide variety of S-substituted cysteine derivatives occur in plant metabolites. For example, S -allyl- l -cysteine (SAC), mainly contained in garlic, gathers huge interest because of its favorable bioactivities for human health. However, conventional methods for preparing SAC suffer from several drawbacks with regard to efficiency and toxicity, which highlights the need for improved processes for SAC synthesis. This study aims to develop a novel bioprocess to produce SAC by microbial enzymes from easily available substrates. We found that Escherichia coli had the ability to synthesize SAC from allyl mercaptan, pyruvic acid, and ammonium sulfate. An enzyme purification through 3-step column chromatography, followed by determination of the N-terminal amino acid sequence revealed that tryptophanase (TnaA) was the enzyme responsible for SAC formation. Although the enzyme catalyzed the reversible reaction for synthesizing and degrading SAC, the degradation proceeded significantly faster than the synthesis. Interestingly, TnaA catalyzed the synthesis of a wide range of S-substituted cysteines with alkyl chains or aromatic rings, some of which are present in Allium and Petiveria plants. Our results showed a novel substrate specificity of TnaA toward various S-substituted cysteine. TnaA is a promising biocatalyst for developing a new process to supply various valuable S-substituted cysteine derivatives for medicinal and health-promoting applications. [ABSTRACT FROM AUTHOR]

We have cloned a gene encoding an aldehyde oxidase (ALOD) oxidized glyoxal but not glyoxylic acid from Pseudomonas sp. AIU 362. The ALOD gene contained an open reading frame consisting of 888 nucleotides corresponding to 295 amino acid residues. The deduced amino acid sequence exhibited a high similarity to those of 3-hydroxyisobutyrate dehydrogenases (3-HIBDHs). We expressed the cloned gene as an active product in Escherichia coli BL21 cells. The productivity (total units per culture broth volume) of the recombinant ALOD expressed in E. coli BL21 was 20,000-fold higher than that of ALOD in Pseudomonas sp. AIU 362. The recombinant ALOD exhibited ALOD activity and 3-HIBDH activity. The 3-HIBDH from Pseudomonas putida KT2440 also exhibited ALOD activity. Thus, the ALOD from Pseudomonas sp. AIU 362 and 3-HIBDH from P. putida KT2440 were classified into the same enzyme group. [ABSTRACT FROM AUTHOR]

Abstract: We have cloned a gene encoding an alcohol oxidase (AOD) specific to aldehyde alcohols from Paenibacillus sp. AIU 311. The AOD gene contains an open reading frame consisting of 618 nucleotides corresponding to 205 amino acid residues. The deduced amino acid sequence exhibits a high similarity to that of manganese superoxide dismutases (SODs). We expressed the cloned gene as an active product in Escherichia coli BL21 cells. The productivity (total units per culture broth volume) of the recombinant AOD expressed in E. coli BL21 is 26,000-fold higher than that of AOD in Paenibacillus sp. AIU 311. The recombinant AOD also exhibits aldehyde alcohol oxidase activity and SOD activity. The recombinant cells described in this study have utility for the production of glyoxal from glycolaldehyde. [Copyright &y& Elsevier]

The relations between oxidase activity on aldehyde alcohols and superoxide dismutase (SOD) were investigated, since the amino terminal amino acid sequence of alcohol oxidase (AOD) from Paenibacillus sp. AIU 311, which was specific to aldehyde alcohols, exhibited high similarity to those of SODs containing manganese (Mn2+-SOD). Paenibacillus AOD had high SOD activity. The SODs containing manganese, iron, or copper and zinc also exhibited oxidase activities on aldehyde alcohols, and the relative values of oxidase activities on aldehyde alcohols to SOD activity of Mn2+-SOD were closer to those of Paenibacillus AOD compared with those of the other SODs. Thus, SODs had AOD activity on aldehyde alcohols as another enzyme activity, and the Paenibacillus AOD and Mn2+-SOD were classified into a similar group. [Copyright &y& Elsevier]