title: Pyridine nucleosidase in bull semen. II. Biochemical properties.
abstract: It is most likely a single enzyme (NAD+ nucleosidase) present in semen from most bulls which hydrolyses the ribosyl pyridinium bond in both NAD and NADP. This conclusion is based on the following results: (i) each of 12 semen samples containing nucleosidase activity hydrolysed NAD at the same rate as NADP (r = 0.99); (ii) other untreated semen samples from different bulls which did not hydrolyse NAD were also inactive against NADP; (iii) enzyme denaturation produced by preliminary heating of semen filtrates for 15 min at varied temperatures or by heating at 55 degrees C for varied time intervals caused similar reductions in the rates of NAD and NADP hydrolysis; and (iv) nicotinamide inhibited enzyme activity to the same degree using either NAD or NADP as the substrate.
mesh_terms: D000818:Animals; D002417:Cattle; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D008297:Male; D009699:N-Glycosyl Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009243:NAD; D009244:NAD+ Nucleosidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009249:NADP; D009536:Niacinamide / Q000494:pharmacology; D012661:Semen / Q000201:enzymology*; D013997:Time Factors
chemical_list: D009243:NAD; D009536:Niacinamide; D009249:NADP; D009699:N-Glycosyl Hydrolases; D009244:NAD+ Nucleosidase