Specificity of Thermophilic Streptomyces Alkaline Proteinase

The specificity of highly purified alkaline proteinase B (EC 3.4.21.14) from thermophilic Streptomyces rectus var. proteolyticus was investigated with an oxidized insulin B chain. Hydrolysis of the oxidized insulin B chain in a 4-hr incubation was observed mainly at three peptide bonds (Phe24-Phe25, Leu15-Tyr16 and Leu11-Val12) and additionally at six others (Leu6-CySO3H7, Gln4-His5, Leu17-Val18, His5-Leu6, Glu13-Ala14, Asn3-Gln4).Hydrolysis of angiotensin (formerly designated angiotensin II) was observed at the Tyr4-Ile5 bond. Hydrolysis of proangiotension (formerly designated angiotensin I) was observed at the Tyr4-Ile5 and Phe8-His9 bonds.