Comparison of the specificities of various neutral proteinases from microorganisms

A comparative study was made of the specificities of six neutral proteinases of microorganisms which originated from Bacillus subtilis, Bacillus thermoproteolyticus, Pseudomonas aeruginosa, Streptomyces griseus, and Aspergillus oryzae against the oxidized insulin B-chain and various synthetic peptides. The major cleavages of the insulin molecule occurred at the peptide bonds of His-Leu, His-Leu, Ala-Leu, Tyr-Leu, 5 6 10 11 14 15 16 17 Gly-Phe, and Phe-Phe by all the enzymes. The experiment with synthetic peptides in 23 24 24 25 dicated that these enzymes preferentially hydrolyzed the peptide bonds containing amino groups of l-leucine and l-phenylalanine. The rates of activities against the both peptide bonds differed depending on the species of enzyme. An enhancement in the rate of hydrolysis was observed by the presence of an alanyl group as the amino acid whose carboxyl group formed the bond in the case of the P. aeruginosa enzyme, while the highest rate was seen by a tyrosyl group in the cases of the other enzymes. The peptidase activity of mold enzyme was considerably smaller in comparison with the bacterial enzymes. These results led to the consideration that neutral proteinases from microorganisms exhibit remarkably similar although not identical specificities irrespective of their origins.