based on the comparison of the catalytic activities of subtilisin and thiol-subtilisin , a rigid active site model for the serine proteases is proposed in which the histidine residue operates in a fixed steric position both as a general base and as a general acid , and this , rather than the formation of a hydrogen bond , accounts for the high nucleophilicity of the serine residue .
C0038601
subtilisin
C0036734
serine proteases