Thymidine phosphorylase and uridine phosphorylase of Lactobacillus casei

Abstract

Crude extracts of Lactobacillus casei, were found to possess both thymidine phosphorylase and uridine phosphorylase activities, which were associated with a single sucrose gradient band. However, using dye ligand chromatography (Green A), two enzymatic fractions were obtained each of which possessed mainly one of these activities. By this procedure, the uridine phosphorylase was purified 329‐fold and the thymidine phosphorylase about 25‐fold. The existence of the two phosphorylases was supported by Km, Ki, pH optimum, and heat stability studies. Identical bands were obtained on sucrose gradient sedimentation for the purified enzymes and for their mixture in a crude extract, suggesting that they have similar sedimentation coefficients, and do not form an aggregate in the crude extract.