Streptomyces griseus protease C. A novel enzyme of the chymotrypsin superfamily.

In this report we describe a novel chymotrypsin-like serine protease produced by Streptomyces griseus.The enzyme has been tentatively named S. griseus protease C (SGPC).The gene encoding the enzyme (sprC) was identified and isolated on the basis of its homology to the previously characterized S. griseus protease B (SGPB).The sprC gene encodes a 457-amino acid prepro-mature protein of which only the 255 carboxyl-termmal amino acids are present in the mature enzyme.Mature SGPC contains two distinct domains connected by a 19-amino acid linker region rich in threonines and prolines.While the amino-terminal domain is homologous to S. griseus proteases A, B, and E and the a-lytic protease of Lysobacter enzymogenes, the carboxyl-terminal domain is not homologous with any known protease.However, the carboxyl-terminal domain shares extensive homology with chitin-binding domains of Bacillus circulans chitinases A1 and D, suggesting that the enzyme is specialized for the degradation of chitin-linked proteins.Recombinant expression and preliminary characterization of the catalytic properties of the enzyme are also reported.The primary specificity of SGPC is similar to that of SGPB; both enzymes preferentially cleave peptide bonds following large hydrophobic side chains.The soil microorganism Streptomyces griseus secretes a variety of hydrolytic enzymes.Consequently, it is the source of a commercial, crude enzyme preparation known as Pronase.Several members of the chymotrypsin-like serine protease family have been purified from Pronase.The corresponding genes have been isolated using synthetic oligonucleotide probes based on the amino acid sequences of the enzymes.Past studies uncovered the enzymes S. griseus protease A (SGPA),' S. griseus protease B (SGPB) (1, 21, S. griseus protease E (SGPE) (3, 4), and S. griseus trypsin (SGT) (1, 5); however, the full breadth and divergence of enzymes secreted from S. griseus has not been determined.As part of an evolutionary study of the S. griseus proteases, we adopted a strategy for cloning protease *