Composition, Properties, and Substrate Specificities of Myxobacter AL-1 Protease

Abstract

Abstract Myxobacter strain AL-1 excretes a bacteriolytic enzyme designated as AL-1 protease. A procedure is described for obtaining homogeneous preparations of the enzyme. Physical studies revealed s020,w = 2.40 S; D020,w = 14 x 10-7 cm2 per sec; [n] = 1.66 ± 0.1 ml per g; a molecular weight of 14,300; frictional coefficient (f/f0) = 1.0. AL-1 protease contains 136 amino acids, a value which corresponds to a minimal molecular weight of 13,977. In contrast to many exocellular enzymes, this protein contains 1 disulfide bond, 1 mole of hexose, a relatively high content of aromatic amino acids, and an E1%1 cm = 15.8 at 280 mµ. The shortest peptide which served as a substrate was a tetrapeptide. Gly-Gly-Gly-Gly yielded Gly-Gly; Gly-Gly-Gly-Gly-Gly yielded Gly-Gly and Gly-Gly-Gly; l-Ala-Gly-Gly-Gly-Gly yielded l-Ala-Gly-Gly and Gly-Gly; Gly-Gly-Gly-Gly-l-Ala yielded Gly-Gly-Gly and Gly-l-Ala; Gly-Gly-l-Ala-Gly-Gly yielded Gly-Gly and l-Ala-Gly-Gly; and N-CBZ-Gly-l-Pro-l-Leu-Gly-l-Pro yielded N-CBZ-Gly-l-Pro and l-Leu-Gly-l-Pro. The hydrolysis points in the oxidized β chain of insulin were Ala-Leu, Val-CySO3H, and Gly-Phe.