Enzymatic Hydrolysis of α- and β-Oligo(L-aspartic acid)s by Poly(aspartic acid) Hydrolases-1 and 2 from Sphingomonas sp. KT-1

✍ Scribed by Tomohiro Hiraishi; Mariko Kajiyama; Ichiro Yamato; Yoshiharu Doi

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 235 KB
• Volume: 4
• Category: Article
• ISSN: 1616-5187
• DOI: 10.1002/mabi.200300085

✦ Synopsis

Abstract

Summary: The enzymatic hydrolysis of α‐ and β‐oligo(L‐aspartic acid)s by PAA hydrolase‐1 and PAA hydrolase‐2 (purified from Sphingomonas sp. KT‐1) was performed to elucidate the mechanism of the microbial degradation by Sphingomonas sp. KT‐1 of the thermally synthesized α,β‐poly(D,L‐aspartic acid) (tPAA). GPC analysis of the hydrolyzed products of α‐ and β‐tetra(L‐aspartic acid)s by PAA hydrolase‐1 has showed that PAA hydrolase‐1 is capable of hydrolyzing only the specific amide bonds between β‐aspartic acid units. The RP‐HPLC analysis of the enzymatic hydrolysis of β‐oligo(L‐aspartic acid)s (4 and 5 mers) by PAA hydrolase‐1 has suggested that the enzymatic hydrolysis of β‐oligo(L‐aspartic acid)s occurs via an endo‐mode cleavage. In contrast, PAA hydrolase‐2 hydrolyzed both α‐ and β‐oligo(L‐aspartic acid)s via an exo‐mode cleavage to yield L‐aspartic acid as a final product. A kinetic study on the enzymatic hydrolysis of α‐oligo(L‐aspartic acid)s (3 to 7 mers) by PAA hydrolase‐2 has indicated that K~m~ values are almost independent of the number of monomer units in oligomers of 4 to 7 mers, while that V~max~ values are markedly dependent on the chain length and show a maximum value at 5 mer.

A proposed mechanism of the enzymatic hydrolysis of tPAA by PAA hydrolase‐1 and PAA hydrolase‐2 in the cell of Sphingomonas sp. KT‐1.

imageA proposed mechanism of the enzymatic hydrolysis of tPAA by PAA hydrolase‐1 and PAA hydrolase‐2 in the cell of Sphingomonas sp. KT‐1.