Extraction of cyclic amide amidohydrolase from green hulls of Pisum sativum and its use as biocatalyst for N-carbamyl amino acids

This work evaluates the potential of different varieties of legumes, Phaseolus vulgaris and Pisum sativum, as a source of a biocatalyst, cyclic amide amidohydrolase, which is used for the in vitro synthesis of N-carbamyl amino acids precursors. For most legumes evaluated, the substrate specificity of the amide amidohydrolase favored hydantoin hydrolysis, as compared to dihydropyrimidine and 5-monosubstituted hydantoins. The green hulls from P. sativum showed hydantoinase activity against hydantoin (34•9 U/g), -5-methylmercaptoethylhydantoin (18•1 U/g) and -5-isopropylhydantoin (5•3 U/g), while the feed culls of P. vulgaris had the highest -5-methylhydantoin-hydrolysing activity (15•1 U/g). Conversion of up to 100% of hydantoin to N-carbamylglycine and of -5-methylhydantoin to N-carbamylalanine was observed within 12 h when the crude hydantoinase from P. sativum variety green field pea was used in a batch-operated bioreactor. Hydantoinase extracted from pea hulls has been shown to be more stable and active at higher temperatures than the microbial hydantoinase from the bacterium Pseudomonas putida. An economic analysis indicates that legume surplus is a cheaper source of hydantoinase than microbial material.