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NAD glycohydrolase activity in dog cardiac tissue
1Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados, Instituto Politécnico Nacional, Mexico, D.F.
Abstract:
1. Dog heart tissue suspension hydrolyzes NAD, NADP and NMN, and releases nicotinamide stoichiometrically. 2. Maximum activity was observed at 50 degrees C and the activation energy was 10 kcal/mol. 3. Optimum pH range was 6.2-7.6. 4. Compounds with adenine-ribose moiety increased the enzymatic activity. 5. Nicotinamide released during incubation produced reaction nonlinearity. 6. Km for NAD and NADP were about the same; Vmax was higher for NAD. Similar findings have been reported for rabbit heart. 7. Dog enzyme appears to be more sensitive than the rabbit enzyme to noncompetitive inhibitors. 8. Pyrophosphatase activity was not detected in dog heart in contrast to rabbit and rat heart preparations.