Tyrostatin

Tyrostatin is a peptide inhibitor isolated from Kitasatospora sp. 55. It has a K_i value of 6 nM against serine carboxyl protease (PSCP) from Pseudomonas sp. 101, a K_i value of 2.1 nM against carboxyl protease (XSCP) from Xanthomonas sp. T-22, and a K_i value of 2.6 nM against carboxyl protease (PCP) from Pseudomonas sp. 101. Tyrostatin forms a reversible covalent hemiacetal bond with Ser287 at the active site of PSCP, where Tyr at the P1 position and Leu at the P2 position occupy the S1-S4 subsites of the enzyme. Tyrostatin inhibits the activity of XSCP, specifically blocks the autocatalytic maturation process of PCP precursor under acidic conditions, and also inhibits the protease activity of mature and recombinant PCP in a dose-dependent manner. Tyrostatin does not inhibit KSCP or alcohol-resistant protease J-4, and can serve as a tool for identifying the catalytic residues of PCP.