Action of the protease from Streptomyces cellulosae on L-Leu-Gly

The protease from Streptomyces cellulosae preferentially catalyzed the formation of (L-Leu-Gly)2 (P1) and (L-Leu-Gly)3 (P2) in highly concentrated solutions of L-Leu-Gly, although it weakly hydrolyzed the substrate at the same time. The formation of P1, P2, L-Leu, and Gly was studied at various pH values, temperatures, and substrate concentrations. The initial velocities (v1, v2, and vH) of formation of P1, P2, and L-Leu (or Gly) and the sum (v1T) of v1 and v2 were determined. The effects of pH and temperature on v1, v2, vH, and v1T were examined at a fixed substrate concentration. The optimum pH and optimum temperature for each of the processes forming P1, P2, L-Leu, and Gly were 8.0 and 65 degrees C, respectively. In the study on the effect of substrate concentration, the plots of the initial velocities versus substrate concentrations were sigmoidal at lower substrate concentrations. The dependence of v1T on the substrate concentration could be explained by a mechanism involving a single active center forming the peptide bonds and two substrate-binding sites located on the left sites (S1 and S2) and the right sites (S1' and S2') of the active center of this enzyme.