원문정보
초록
영어
Molecular modeling and site-directed mutagenesis were used to probe the molecular determinants of substrate specificity for aliphatic and aromatic nitriles of nitrilase from Rhodococcus rhodochrous tg1-A6. Ten putative expected substrate-binding residues within 4.5 Å of active site were replaced with respective Ala and then only the substitution of position 142 resulted in the high activity at aromatic substrates but no activity at aliphatic substrates. When Tyr-142 was further mutated to glycine, valine, leucine, isoleucine, serine, asparagine, arginine, aspartic acid and phenylalanine respectively, interestingly uncharged and smaller amino acid substituted mutants exhibited higher catalytic efficiency with aromatic substrates than the wild-type enzyme exhibited. Whereas smaller amino acid substituted mutants had no activity on aliphatic substrates. These results Tyr-142 position modulated substrate specificity of aromatic
and aliphatic substrates.