Abstract

Nucleotidase activities resembling subclass I and subclass II of human pyrimidine 5nucleotidases (P5N) were detected in chicken red blood cells (RBCs). In chicken RBCs from untreated controls, the activity of the subclass II enzyme was about one third of that of subclass I enzyme, whereas that ratio was approximately 5:1 in rat or human RBCs. The subclass I activity in chicken RBCs was increased 5- to 6- fold upon erythropoietic induction by phenylhydrazine administration, but the subclass II activity did not increase under these conditions. The subclass I enzyme was purified to near homogeneity. Its molecular mass was about 35 kDa as estimated by gel filtration and SDSpolyacrylamide gel electrophoresis. Its Nterminal 12 amino acids, PEFQKKTVHIKD, were also determined. The catalytic properties of the subclass I enzyme were very similar to those of the human enzyme with regard to substrate (preferential hydrolysis of CMP, dCMP, UMP), K values, optimum pH, and metal ion requirements. Antibodies against chicken P5N subclass I were raised in rats. The chicken P5NI as well as the rat P5NI proteins could be detected by antibodies in Western blot analyses, but not the P5NII proteins. These findings indicate that P5N subclass I may have an important function in chicken erythropoiesis.