A Simple Enzymatic Method for Production of a Wide Variety of D-Amino Acids Using L-Amino Acid Oxidase from Rhodococcus sp. AIU Z-35-1

A simple enzymatic method for production of a wide variety of D-amino acids was developed by kinetic resolution of DL-amino acids using L-amino acid oxidase (L-AAO) with broad substrate specificity from Rhodococcus sp. AIU Z-35-1. The optimum pH of the L-AAO reaction was classified into three groups depending on the L-amino acids as substrate, and their respective activities between pH 5.5 and 8.5 accounted for more than 60% of the optimum activity. The enzyme was stable in the range from pH 6.0 to 8.0, and approximately 80% of the enzyme activity remained after incubation at 40°C for 60 min at pH 7.0. D-Amino acids such as D-citrulline, D-glutamine, D-homoserine or D-arginine, which are not produced by D-aminoacylases or D-hydantoinases, were produced from the racemic mixture within a 24-hr reaction at 30°C and pH 7.0. Thus, the present method using L-AAO was versatile for production of a wide variety of D-amino acids

Characterization of a novel hydroxynitrile lyase from <i>Nandina domestica</i> Thunb

<p>The leaves of <i>Nandina domestica</i> Thunb. exhibited high hydroxynitrile lyase (HNL) activity in (<i>R</i>)-mandelonitrile synthesis. The specific activity of young leaves was significantly higher than that of mature leaves. We isolated two HNLs with molecular mass of 24.9 kDa (<i>Nd</i>HNL-S) and 28.0 kDa (<i>Nd</i>HNL-L) from the young leaves. Both <i>Nd</i>HNLs were composed of two identical subunits, without FAD and carbohydrates. We purified <i>Nd</i>HNL-L and revealed its enzymatic properties. The whole deduced amino acid sequence of <i>Nd</i>HNL-L was not homologous to any other HNLs, and the specific activity for mandelonitrile synthesis by <i>Nd</i>HNL-L was higher than that by other plant HNLs. The enzyme catalyzed enantioselective synthesis of (<i>R</i>)-cyanohydrins, exhibited high activity at pH 4.0, and high stability in the pH range of 3.5–8.0 and below 55°C. Thus, <i>Nd</i>HNL-L is a novel HNL with novel amino acid sequence and has a potential for the efficient production of (<i>R</i>)-cyanohydrins.</p> <p>Leaves of <i>Nandina domestica</i> Thunb. showing high R-hydroxynitrile lyase (HNL) activity.</p