Neutral protease from Bacillus subtili

The zinc ion in a neutral protease from Bacillus subtilis has been exchanged with other metal ions (139—141). The Co(II) enzyme is reported to be active (140). 

Many related so-called thermolysin-like proteinases (TLPs) from various Grampositive strains have been described [47], including neutral proteases from Bacillus subtilis, and some of these variants are applied in peptide synthesis. Several metal-loenzymes acting as carboxy- or aminopeptidase have also been characterized, but these variants have not been extensively used in peptide synthesis. A bovine carboxy-peptidase A [39] and orange carboxypeptidase C [68] have been applied for dipeptide synthesis in water-organic solvent mixtures, both under thermodynamic and xmder kinetic control. 

In the brewing industry, there is a development toward substitution of malt with unmalted barley and amylase, by use of glu-canase and protease of microbial origin. The neutral protease from Bacillus amyloliquefaciens and the thermostable neutral protease Bacillus subtilis var. thermoproteolyticus have been used by brewers successfully to hydrolyze barley proteins into amino acids and peptides. 

Thermolysin belongs to a class of proteases (called neutral proteases) which are distinct from the serine proteases, sulfhydryl proteases, metal-loexopeptidases, and acid proteases. Neutral proteases A and B from Bacillus subtilis resemble thermolysin in molecular weight, substrate specificity, amino acid content, and metal ion dependence. Since physiological substrates are most likely proteins, it is difficult to design simple experiments that can be interpreted in terms of substrate specificity and relative velocities. Therefore, studies of substrate specificity and other kinetic parameters must be carried out on di- and tripeptides so that details of the mechanism of catalysis can be obtained and interpreted simply. 

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