Abstract: The present invention has its object to provide a method for producing an L-amino acid comprising reacting a keto acid with an amino acid dehydrogenase and an enzyme having coenzyme regenerating ability to convert to a L-amino acid, wherein a coenzyme is added in two or more portions in the reaction. The method of the present invention enables efficient production of an L-amino acid useful as a synthetic intermediate such as a pharmaceutical intermediate with high optical purity by an enzymatic reductive amination independent of the purity of the keto acid used as a substrate.

Abstract: The present invention provides a simple industrial process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, which is a useful pharmaceutical intermediate, from readily available, inexpensive raw materials. In a process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, a racemic N-carbamoyl-?-methylcysteine derivative or its salt is D-selectively cyclized with hydantoinase to produce a D-5-methyl-5-thiomethylhydantoin derivative or its salt and an N-carbamoyl-?-methyl-L-cysteine derivative or its salt, which are then subjected to deprotection of the amino group and the sulfur atom, and hydrolysis.

Abstract: The present invention provides a simple industrial process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, which is a useful pharmaceutical intermediate, from readily available, inexpensive raw materials. In a process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, a racemic N-carbamoyl-?-methylcysteine derivative or its salt is D-selectively cyclized with hydantoinase to produce a D-5-methyl-5-thiomethylhydantoin derivative or its salt and an N-carbamoyl-?-methyl-L-cysteine derivative or its salt, which are then subjected to deprotection of the amino group and the sulfur atom, and hydrolysis.

Abstract: The present invention relates to a method for reducing the relative ratio of 3-hydroxy-3?,4?-didehydro- ?, ?-caroten-4-one (HDCO) to astaxanthin in a composition containing astaxanthin and HDCO by contacting the composition with an acidic medium having a pH of 3 or less and/or a basic medium having a pH of 9 or greater, and also relates to a method for producing an astaxanthin-containing composition which includes reducing the relative ratio of HDCO by the above method. By means of the method of the present invention, the relative ratio of HDCO, the biological function of which is not known, in an astaxanthin-containing composition can be easily reduced.

Abstract: The present invention relates to novel D-amino acid oxidase isolated and purified from Candida intermedia, a gene encoding the D-amino acid oxidase, a recombinant plasmid containing the gene, and a transformant into which the D-amino acid oxidase gene has been introduced, as well as a production method of D-amino acid oxidase including culturing the transformant. Moreover, the present invention relates to a production method of L-amino acids, 2-oxo acids or cyclic imines, which include reacting racemic amino acids with the D-amino acid oxidase, more preferably, a production method of L-amino acids, which includes reacting racemic amino acid with the D-amino acid oxidase, amino acid dehydrogenase and an enzyme having a coenzyme-regenerating activity. According to the present invention, L-amino acids, 2-oxo acids or cyclic imines can be produced with good efficiency in an industrial scale.

Abstract: The present invention relates to novel D-amino acid oxidase isolated and purified from Candida intermedia, a gene encoding the D-amino acid oxidase, a recombinant plasmid containing the gene, and a transformant into which the D-amino acid oxidase gene has been introduced, as well as a production method of D-amino acid oxidase including culturing the transformant. Moreover, the present invention relates to a production method of L-amino acids, 2-oxo acids or cyclic imines, which include reacting racemic amino acids with the D-amino acid oxidase, more preferably, a production method of L-amino acids, which includes reacting racemic amino acid with the D-amino acid oxidase, amino acid dehydrogenase and an enzyme having a coenzyme-regenerating activity. According to the present invention, L-amino acids, 2-oxo acids or cyclic imines can be produced with good efficiency in an industrial scale.

Abstract: The present invention provides a simple industrial process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, which is a useful pharmaceutical intermediate, from readily available, inexpensive raw materials. In a process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, a racemic N-carbamoyl-?-methylcysteine derivative or its salt is D-selectively cyclized with hydantoinase to produce a D-5-methyl-5-thiomethylhydantoin derivative or its salt and an N-carbamoyl-?-methyl-L-cysteine derivative or its salt, which are then subjected to deprotection of the amino group and the sulfur atom, and hydrolysis.

Abstract: Disclosed are a novel hydantoin racemase and a process for producing an optically active N-carbamylamino acid or an optically active amino acid using the hydantoin racemase. A novel hydantoin racemase isolated and purified from Bacillus sp. Strain KNK519HR; a gene encoding the hydantoin racemase; a recombinant plasmid having the gene introduced therein; a transformant having the hydantoin racemase gene introduced therein; and a process for producing an optically active N-carbamylamino acid or an optically active amino acid characterized in that a 5-substituted hydantoin compound is treated in the presence of hydantoinase and N-carbamylamino acid amidohydrolase as well as the hydantoin racemase.

Abstract: The present invention has its object to provide a method for producing an L-amino acid comprising reacting a keto acid with an amino acid dehydrogenase and an enzyme having coenzyme regenerating ability to convert to a L-amino acid, wherein a coenzyme is added in two or more portions in the reaction. The method of the present invention enables efficient production of an L-amino acid useful as a synthetic intermediate such as a pharmaceutical intermediate with high optical purity by an enzymatic reductive amination independent of the purity of the keto acid used as a substrate.

Abstract: It is an object of the present invention to provide a novel amidase that is useful for production of an optically active amino acid, and in particular, a D-amino acid, and a production method thereof. The present invention relates to a novel D-amidase isolated and purified from the Arthrobacter sp. KNK1101J, a gene encoding the above amidase, a recombinant plasmid comprising the above gene, and a transformant into which the above amidase gene has been introduced. In addition, the present invention also relates to a method for producing the amidase, comprising culturing the Arthrobacter sp. KNK1101J or the above transformant, and collecting the above amidase.

Abstract: It is an object of the present invention to provide a novel amidase that is useful for production of an optically active amino acid, and in particular, a D-amino acid, and a production method thereof. The present invention relates to a novel D-amidase isolated and purified from the Arthrobacter sp. KNK1101J, a gene encoding the above amidase, a recombinant plasmid comprising the above gene, and a transformant into which the above amidase gene has been introduced. In addition, the present invention also relates to a method for producing the amidase, comprising culturing the Arthrobacter sp. KNK1101J or the above transformant, and collecting the above amidase.

Abstract: Disclosed are a novel hydantoin racemase and a process for producing an optically active N-carbamylamino acid or an optically active amino acid using the hydantoin racemase. A novel hydantoin racemase isolated and purified from Bacillus sp. Strain KNK519HR; a gene encoding the hydantoin racemase; a recombinant plasmid having the gene introduced therein; a transformant having the hydantoin racemase gene introduced therein; and a process for producing an optically active N-carbamylamino acid or an optically active amino acid characterized in that a 5-substituted hydantoin compound is treated in the presence of hydantoinase and N-carbamylamino acid amidohydrolase as well as the hydantoin racemase.

Abstract: The invention provides a formate dehydrogenase having high specific activity, small Km values for formate and NAD, broad temperature and pH ranges of stability, broad temperature and pH ranges for action, and capable of regenerating a coenzyme with good efficiency in case of being present in an enzymatic reduction reaction system without inactivated. The invention provides the enzyme mentioned above which has characteristics suited for industrial application by screening for soil formate dehydrogenase-producing microorganisms. The invention further provides a DNA containing the gene coding for the enzyme of the invention, a recombinant DNA constructed using a vector, and a transformant obtained by using this plasmid.

Abstract: A process for conveniently and industrially producing an optically active ?-methylcysteine derivative, which is useful as an intermediate of medicines and the like, from an inexpensive and readily available material is provided. The present invention relates to a process for producing a racemic or optically active ?-methylcysteine derivative including a step of hydrolyzing a racemic or optically active N-carbamyl-?-methylcysteine derivative by treating with decarbamylase, and a process for producing an optically active ?-methylcysteine derivative and an optically active N-carbamyl-?-methylcysteine derivative having a configuration opposite to that of the compound including a step of stereoselectively hydrolyzing a racemic N-carbamyl-?-methylcysteine derivative by treating with decarbamylase.

Abstract: The present invention provides a simple industrial process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, which is a useful pharmaceutical intermediate, from readily available, inexpensive raw materials. In a process for producing an L- or D-optically active ?-methylcysteine derivative or its salt, a racemic N-carbamoyl-?-methylcysteine derivative or its salt is D-selectively cyclized with hydantoinase to produce a D-5-methyl-5-thiomethylhydantoin derivative or its salt and an N-carbamoyl-?-methyl-L-cysteine derivative or its salt, which are then subjected to deprotection of the amino group and the sulfur atom, and hydrolysis.

Abstract: A process for easily producing an L-?-methylcysteine derivative or its salt, which is useful as a drug intermediate, from a cheap easily procurable raw material through an enzymatic D-stereoselective hydrolysis of racemic 5-halomethyl-5-methyl-hydantoin. L-?-methylcysteine derivative or its salt is produced by converting racemic 5-halomethyl-5-methylhydantoin to L-5-halomethyl-5-methylhydantoin through an enzymatic D-stereoselective hydrolysis, reacting the L-5-halomethyl-5-methylhydantoin with a sulfurizing agent into L-5-methyl-5-thiomethylhydantoin and hydrolyzing the L-5-methyl-5-thiomethylhydantoin.

Abstract: The invention provides a formate dehydrogenase having high specific activity, small Km values for formate and NAD, broad temperature and pH ranges of stability, broad temperature and pH ranges for action, and capable of regenerating a coenzyme with good efficiency in case of being present in an enzymatic reduction reaction system without inactivated. The invention provides the enzyme mentioned above which has characteristics suited for industrial application by screening for soil formate dehydrogenase-producing microorganisms. The invention further provides a DNA containing the gene coding for the enzyme of the invention, a recombinant DNA constructed using a vector, and a transformant obtained by using this plasmid.

Abstract: A DNA fragment coding for a decarbamylase protein improved in thermostability as the result of replacement of at least one base of a DNA fragment coding for a decarbamylase protein derived from a microorganism with another base and the resultant replacement of at least one of the corresponding amino acids, and its production process; a vector containing the DNA fragment; a transformant obtained by transformation with the vector; as well as a decarbamylase improved in thermostability and its production process. Also disclosed is a process for producing a D-.alpha.-amino acid, which comprises converting an N-carbamoyl-D-.alpha.-amino acid into the corresponding D-.alpha.-amino acid in an aqueous medium by the action of a decarbamylase having a thermostable temperature of 65.degree. C. or higher; and collecting the D-.alpha.-amino acid produced.

Abstract: A process for the efficient production of a D-amino acid from the corresponding DL-5-substituted hydantoin by one-step reaction which comprises using a composite immobilized enzyme at a pH about neutrality, said composite immobilized enzyme being obtained by immobilizing a hydantoinase having its optimal pH within an alkaline range and a D-N-carbamyl-.alpha.-amino acid amidohydrolase having its optimal pH about neutrality in a coexisting state on an immobilizing support, simultaneously, is disclosed.

Abstract: In a process for the production of a D-.alpha.-amino acid, in which an N-carbamyl-D-.alpha.-amino acid corresponding to the general formula: ##STR1## wherein R represents phenyl, hydroxy-substituted phenyl, substituted or unsubstituted alkyl, or thienyl, is converted by a microbial enzyme in an aqueous medium to a D-.alpha.-amino acid corresponding to the general formula: ##STR2## wherein R is the same as defined above, decarbamylase produced by a microorganism of the genus Comamonas, Blastobacter, Alcaligenes, Sporosarcina, Rhizobium, Bradyrhizobium or Arthrobacter is used as the enzyme converting the N-carbamyl-D-.alpha.-amino acid to the D-.alpha.-amino acid.The conversion of the N-carbamyl-D-.alpha.-amino acids to the D-.alpha.-amino acids is carried out in a neutral to alkaline pH range.