Substrate Specificities of the Proteases from a Marine-psychrophilic Bacterium, Pseudomonas sp. No. 548

The specificities of the alkaline and neutral proteases from the marine-psychrophilic Pseudomonas sp. No. 548 were investigated using oxidized insulin B-chain and various synthetic peptides as substrates. The alkaline protease was able to cleave the peptide or amide bonds containing a carboxyl group of amino acid residues, such as l-alanine, l-glutamic acid, l-arginine, l-leucine, l-phenylalanine, l-tryptophan, l-tyrosine, and l-valine. On the basis of the specificities, the enzyme might be classified as a serine protease, comparing the specificities of the proteases so far reported, although the enzyme is inactivated with ethylenediamine tetraacetic acid as well as diisopropylfluorophosphate.The neutral protease catalized the hydrolysis of the peptide bonds containing an amino group of hydrophobic amino acid residues, such as l-isoleucine, l-leucine, and l-phenylalanine. These specificities agree closely with those of the neutral proteases which have been reported.