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KMID : 0376219700070020159
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Chonnam Medical Journal
1970 Volume.7 No. 2 p.159 ~ p.168
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Adenosine Diphosphate Ribose Pyrophosphohydrolase from Rabbit Erythrocytes
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Abstract
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A soluble enzyme has been isolated and partially purified from rabbit erythrocytes which catalyzes the hydrolysis of adenosine diphosphate-5´-ribose (ADP-5´-ribose) to yield AMP and ribose-5´ phosphate:
ADP-5´-ribose+H_(2)O→AMP+Ribose-5´-phosphate
This enzyme shows optimal pH around 9.5 and requires Mg^(2+) and phosphate for the activity, the maximal activity being attained at 5 mM MgCI_(2) and 20 mM phosphate, It is heat-labile, being completely inactivated by heat-treatment at 60℃ for 10 minutes. The inactivation occurs even during storage at 4˚ of the purified enzyme but can be prevented by the presence of 5 mM MgCl_(2)
The enzyme is highly specific for ADP-5´-ribose as substrate and does not attack the pyrophosphate bonds of NAD, ATP and inorganic pyrophosphate. The apparent Michaelis constant for ADP-5´-ribose is 0.57mM.
A potent inhibitor of the enzyme is ADP which acts as a competitive inhibitor. Adenosine mono and triphosphate, inorganic pyrophosphate, oxidized and reduced NAD, and ribose-5´-phosphate are almost not inhibitory.
Since the enzyme can be widely detected in the erythrocytes, spleen, kidney, liver, brain, and muscle, it is suggested that the enzyme may play an important role in metabolic controls of NAD and ADP as well as of ADP-5´-ribose.
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