The Enzyme Database

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Accepted name: hydantoin racemase
Reaction: D-5-monosubstituted hydantoin = L-5-monosubstituted hydantoin
Glossary: hydantoin = imidazolidine-2,4-dione
Other name(s): 5′-monosubstituted-hydantoin racemase; HyuA; HyuE
Systematic name: D-5-monosubstituted-hydantoin racemase
Comments: This enzyme, along with N-carbamoylase (EC and EC and hydantoinase, forms part of the reaction cascade known as the "hydantoinase process", which allows the total conversion of D,L-5-monosubstituted hydantoins into optically pure D- or L-amino acids [7]. The enzyme from Pseudomonas sp. (HyuE) has a preference for hydantoins with aliphatic substituents, e.g. D- and L-5-(2-methylthioethyl)hydantoin, whereas that from Arthrobacter aurescens shows highest activity with arylalkyl substituents, especially 5-benzylhydantoin, at the 5-position [2]. In the enzyme from Sinorhizobium meliloti, Cys76 is responsible for recognition and proton retrieval of D-isomers, while Cys181 is responsible for L-isomer recognition and racemization [6].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
1.  Watabe, K., Ishikawa, T., Mukohara, Y. and Nakamura, H. Purification and characterization of the hydantoin racemase of Pseudomonas sp. strain NS671 expressed in Escherichia coli. J. Bacteriol. 174 (1992) 7989–7995. [PMID: 1459947]
2.  Wiese, A., Pietzsch, M., Syldatk, C., Mattes, R. and Altenbuchner, J. Hydantoin racemase from Arthrobacter aurescens DSM 3747: heterologous expression, purification and characterization. J. Biotechnol. 80 (2000) 217–230. [PMID: 10949312]
3.  Martínez-Rodríguez, S., Las Heras-Vázquez, F.J., Mingorance-Cazorla, L., Clemente-Jiménez, J.M. and Rodríguez-Vico, F. Molecular cloning, purification, and biochemical characterization of hydantoin racemase from the legume symbiont Sinorhizobium meliloti CECT 4114. Appl. Environ. Microbiol. 70 (2004) 625–630. [PMID: 14711700]
4.  Martínez-Rodríguez, S., Las Heras-Vázquez, F.J., Clemente-Jiménez, J.M. and Rodríguez-Vico, F. Biochemical characterization of a novel hydantoin racemase from Agrobacterium tumefaciens C58. Biochimie 86 (2004) 77–81. [PMID: 15016445]
5.  Suzuki, S., Onishi, N. and Yokozeki, K. Purification and characterization of hydantoin racemase from Microbacterium liquefaciens AJ 3912. Biosci. Biotechnol. Biochem. 69 (2005) 530–536. [PMID: 15784981]
6.  Martínez-Rodríguez, S., Andújar-Sánchez, M., Neira, J.L., Clemente-Jiménez, J.M., Jara-Pérez, V., Rodríguez-Vico, F. and Las Heras-Vázquez, F.J. Site-directed mutagenesis indicates an important role of cysteines 76 and 181 in the catalysis of hydantoin racemase from Sinorhizobium meliloti. Protein Sci. 15 (2006) 2729–2738. [PMID: 17132860]
7.  Altenbuchner, J., Siemann-Herzberg, M. and Syldatk, C. Hydantoinases and related enzymes as biocatalysts for the synthesis of unnatural chiral amino acids. Curr. Opin. Biotechnol. 12 (2001) 559–563. [PMID: 11849938]
[EC created 2008]

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