Abstract:The substrate specificity of aminopeptidase from the recombinant Bacillus subtilis was investigated by employing nine types of p-nitroanilide derivatives of amino acids as substrates. The results indicated that the aminopeptidase shows the highest acitivity for Leu-pNA,whose amino acid moiety is hydrophobic leucine. The enzyme also shows high hydrolytic activity to Arg-pNA and Lys-pNA,whose amino acid moieties are basic amino acids. Followed are Ala-pNA,Ile-pNA,ValpNA,Phe-pNA and Pro-pNA,which contain hydrophobic amino acid moiety. However,Glu-pNA which contains acidic amino acid moiety can hardly be hydrolyzed. Then the hydrolysis of corn protein was carried out by the combination of aminopeptidase and endoprotease. With the hydrolysis degree as index by using the single factor experiment,aminopeptidase combined with alkaline protease obtained high efficiency:(1) The content of free amino acid was 4.89 times and 6.05 times than that of alkaline protease aminopeptidase was used alone,respectively.(2)The molecular weight of the peptides was mostly less than 1 000 Da,14.57% is within 500 ~1 000 Da,and 68.42% is within 180~500 Da.(3)The hydrolysis degree was 65%. These results suggested that aminopeptidase combined with alkaline protease hydrolyzes protein raw material.
