Evidence of homologous relationship between thermolysin and neutral protease A of Bacillus subtilis

Abstract

A comparison of the partial amino-acid sequence of neutral protease A from Bacillus subtilis with the structure of thermolysin (EC 3.4.24.4) from Bacillus thermoproteolyticus reveals that these two proteins are homologous. Of 171 residues placed in neutral protease (54% of the sequence), 83 residues (49%) occur in identical positions in thermolysin, and include nine of the 13 residues previously identified as components of the active site of thermolysin. This similarity provides support for the hypothesis that the two enzymes have similar three-dimensional structures and a common mechanism of action. Since these enzymes differ markedly in their resistance to heat inactivation, a comparison of their structures may eventually provide a chemical basis for explaining the differences in their thermal stability.