Intracellular serine proteinase of Bacillus subtilis strain Marburg 168. Comparison with the homologous enzyme from Bacillus subtilis strain A-50.

Intracellular serine proteinase was isolated from sporulating cells of Bacillus subtilis Marburg 168 by gramicidin S-Sepharose 4B affinity chromatography. The enzymological characteristics, the amino acid composition and the 19 residues of the N-terminal sequence of the enzyme are reported. The isolated proteinase was closely related to, but not completely identical with, the intracellular serine proteinase of B. subtilis A-50. The divergence between these two intracellular enzymes was less than that between the corresponding extracellular serine proteinases (subtilisins) of types Carlsberg and BPN′!, produced by these bacterial strains. This may be connected with the more strict selection constraints imposed in intracellular enzymes during evolution.