NAD glycohydrolase: enzyme characterization using intact mammalian erythrocytes.

1. NADase activity has been determined on intact erythrocytes of several species. 2. Although a wide range in maximum velocity exists across species, Michaelis constants observed are very similar. 3. The enzyme is found on the outer surface of the erythrocyte plasma membrane. 4. It is inhibited by substrate after an apparent permanent modification. 5. This modification may be due to self ADP-ribosylation. 6. We have also demonstrated the presence of an ADP-ribosyltransferase on the outer surface of the sheep erythrocyte membrane.