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Substrate Specificity of the Intracellular Proteinase from a Slow Acid Producing Mutant of Streptococcus lactis

Department of Food Science, North Carolina State University Raleigh 27607

ABSTRACT

Substrate specificity of the enzyme of the slow acid producing mutant of Streptococcus lactis No. 3 was examined using the performic acid oxidized beta-chain of insulin as substrate. The action of the enzyme on insulin resulted in the liberation of seven amino acids. Phenylalanine was released early followed by leucine, histidine, tyrosine, valine, alanine, and lysine. Sites of hydrolysis accounting for the release of the seven amino acid residues were determined. The peptide bonds involving the leucyl or phenylalanyl residues were hydrolyzed most rapidly. Specificity of the intracellular proteinase of the mutant differed significantly from that reported for the parent intracellular proteinase.

¹ Present address: Department of Dairy Science, University of Maryland, College Park, Maryland 20742.

² Present address: Dental Research Unit, Veterans Administration Hospital and Institute of Oral Biology, University of Miami, Miami, Florida 33125.