ENZYME

ENZYME entry: EC 5.1.99.5

Accepted Name

Hydantoin racemase.

Alternative Name(s)

5'-monosubstituted-hydantoin racemase.

Reaction catalysed

D-5-monosubstituted hydantoin <=> L-5-monosubstituted hydantoin

Comment(s)

This enzyme, along with EC 3.5.1.77, EC 3.5.1.87 and EC 3.5.2.2, 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.
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.
In the enzyme from Sinorhizobium meliloti, Cys-76 is responsible for recognition and proton retrieval of D-isomers, while Cys-181 is responsible for L-isomer recognition and racemization.

Cross-references

BRENDA

EC2PDB

ExplorEnz

PRIAM enzyme-specific profiles

KEGG Ligand Database for Enzyme Nomenclature

IUBMB Enzyme Nomenclature