Substrate specificity of mammalian pyridine nucleotide transglycosidases

Spectrophotometrical analysis of pyridine nucleotide transglycosidase in mammalian tissues indicated that the enzyme activity was observed to be distributed ubiquitously among the mammalian tissues analyzed, although the velocity ratio of transglycosidation/hydrolysis (vT/vH) and the partitioning of nicotinic acid against water differed with the pyridine nucleotide substrate and the mammalian species, and also with the organ from which the enzyme was extracted. A clarification of their enzymatic properties reveals that pyridine nucleotide transglycosidases were purified from rabbit spleen and guinea pig spleen, after which a kinetic analysis of the transglycosidases was performed. The resulting values, including Km, maximal transglycosidation velocity, and vT/vH, indicated that the enzymes differ in their substrate specificities toward pyridine nucleotide and pyridine base structures.