Substrate Specificity of the Protease from Streptomyces cellulosae

The substrate specificity and the mode of action of the protease from Streptomyces cellulosae were investigated, using many kinds of peptides and proteins as substrates. The protease hydrolyzed peptides consisting of hydrophobic amino acids such as L-Phe-L-Leu-NH₂, L-Pro-L-Phe-NH₂, l-Leu-L-Met, L-Leu-L-Leu, Gly-L-Ile, L-Phe-L-Phe, L-Pro-L-Leu-Gly-NH₂, etc. The protease hydrolyzed zein best among the proteins tested, but weakly hydrolyzed gelatin, myoglobin, bovine serum albumin, γ-globulin, and collagen. The protease mainly hydrolyzed Ser¹²-Leu¹³, Leu¹³-Tyr¹⁴, and Tyr¹⁴-Gln¹⁵ bonds in the oxidized A-chain of insulin and at least the Leu¹⁵-Tyr¹⁶ bond in the oxidized B-chain of insulin.