Cyclic amide amidohydrolases

D-hydantoinase (EC 3.5.2.2) has been identified as one of the main biocatalysts currently on the market in the fine chemicals industry. The market estimate for using the hydantoinase to produce D-p-hydroxyphenylglycine was US 2 million in 1988. D-hydantoinase (EC 3.5.2.2) is a cyclic amide amidohydrolase opening stereoselectively carbon-nitrogen bonds of cyclic amides such as the dihydropyrimidine and hydantoin rings and 5 -monosubstituted hydantoins. The latter are hydrolysed by D-hydantoinase into N-carbamyl D-amino acids which can be converted chemically or enzymically (N-carbamyl-amidohydrolase, EC 3.5.1.6) to optically active amino acids (Figure 1). 

Cyclic Amide Amidohydrolase Agar Assay. Microbial strains obtained from the German Collection of Microorganisms were inoculated in recommended DSM medium supplemented with 1 g/1 hydantoin (Sigma Chemical Co., MO., USA). They were then streaked and further inoculated as single colonies on solid medium (2% agar pH 7.0) containing per litre 5 g... 

Microorganisms tested for cyclic amide amidohydrolase activity (substrate used)... 

Other Cyclic Amide Amidohydrolases and Their Molecular Evolution... 

Figure 5 Reactions catalyzed by cyclic amide amidohydrolases. (a) imidase (b) A/-methylhydan-toin amidohydrolase (c) dihydroorotase (d) allantoinase.

Natural cyclic amides such as 5,6-dihydrouracil, uracil and 5,6-dihydrothymine as well as hydantoin, 5-methylhydantoin and 5-hydroxymethylhydantoin are effective inducers for enzyme biosynthesis (for a more detailed review on induction experiments see reference13 ). In some cases, the dihydropyrimidinase (D-hydantoinase) is associated with an N-carbamoyl-D-amino acid amidohydrolase (D-carbamoylase) and a hydantoin racemase1301. The previously proposed identity of the D-N-carbamoylase with the p-ureidopropionase (E. C. 3.5.1.6), which was assumed to be responsible for the hydrolysis of N-carbamoyl-P-alanine (see Fig. 12.4-7) 131-351 is no longer valid since the investigations of Ogawa et al. on different aerobic bacteria showed that the... 

Recently, the complete amino acid sequences of the various cyclic amide amidohy-drolases were reported and their homology search revealed that D-hydantoinase and ATP-independent l- and DL-hydantoinase are the members of superfamily of amidohydrolases related to ureases [55]. The superfanuly includes dihydropyrimidinase, allantoinase, dihydroorotase, but not ATP-dependent hydantoinases. As a particular sequence, one aspartic... 

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