RT Journal Article
SR Electronic
T1 Purification and Properties of Rat Heart 5'-Nucleotidase
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 641
OP 648
VO 6
IS 6
A1 MERILYN J. EDWARDS
A1 M. HELEN MAGUIRE
YR 1970
UL http://molpharm.aspetjournals.org/content/6/6/641.abstract
AB 5'-Nucleotidase (EC 3.1.3.5) has been purified 26-fold from rat heart and obtained substantially free of nonspecific phosphatase activity. The pH optimum for the enzyme was 7.6; at this pH, 7 mM Mg++ and 2 mM Ca++ caused 40% inhibition of 5'-nucleotidase activity, and 0.17-0.69 mM Mg++ was without effect on activity. The nucleoside triphosphates ATP, UTP, CTP, GTP, and ITP inhibited 5'-nucleotidase in a noncompetitive manner with respect to adenosine 5'-monophosphate. The AMP analogues adenosine 5'-phosphorothioate (AMPS) and 2-chloroadenosine 5'-monophosphate (2-chloro-AMP), which are vasodilators, and 2-methylthioadenosine 5'-monophosphate (2-methylthio-AMP), which has no vasodilatory properties, were all substrates of 5'-nucleotidase, with Michaelis constants similar to that of AMP. The maximum velocities of hydrolysis of AMPS, 2-chloro-AMP, and 2-methylthio-AMP were 36%, 79%, and 116%, respectively, of the maximum velocity for AMP. The rates of hydrolysis of these analogues by 5'-nucleotidase are considered in relation to their vasodilatory effects. ACKNOWLEDGMENT The authors wish to thank Dr. W. J. O’Sullivan of the Department of Medicine, University of Sydney, for his calculations of MgAMP concentrations.