5'-Nucleotidase from rat heart membranes. Inhibition by adenine nucleotides and related compounds.
ADP and ATP and their analogues were evaluated as inhibitors of 5'-nucleotidase purified from heart plasma membrane. ADP analogues are more powerful inhibitors than the corresponding ATP analogues. The most powerful inhibitor found is adenosine 5'-[alpha beta-methylene]diphosphate (AOPCP) for which the enzyme shows a Ki of 5 nM at pH 7.2. Measurements of pKi values for ADP and AOPCP as a function of pH indicate that the major inhibitory species of both nucleotides is the dianion. In the physiological range of pH values, AOPCP is a more powerful inhibitor than ADP principally because a higher percentage of AOPCP exists in the dianion form. The methylenephosphonate analogue of AMP (ACP), though not a substrate, is a moderately effective inhibitor. The corresponding analogues of ADP (ACPOP) and ATP (ACPOPOP) are as good inhibitors as ADP and ATP respectively. The thiophosphate analogues of ADP all inhibit 5'-nucleotidase, although not as powerfully as ADP, the most effective of these analogues being adenosine 5'-O-(1-thiodiphosphate) diastereoisomer B (ADP[alpha S](B)]. Other nucleotides inhibit the enzyme, but none is as effective as AOPCP. Inorganic tripolyphosphate and methylenediphosphonate are better inhibitors of the enzyme than is inorganic pyrophosphate. Inorganic thiophosphate is a better inhibitor than is orthophosphate. Hill plots of the ADP and AOPCP inhibition yield slopes close to 1; Hill plots of the ATP inhibition yield slopes of about 0.6. MgADP- is not an inhibitor, and MgATP2- is at best a very weak inhibitor of the enzyme.
Naito
Y
Y
Lowenstein
J M
JM
D015720:5'-Nucleotidase; D000227:Adenine Nucleotides / Q000494:pharmacology*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology*; D009708:Nucleotidases / Q000037:antagonists & inhibitors*; D051381:Rats
D000227:Adenine Nucleotides; C523965:alpha,beta-methyleneadenosine 5'-diphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D009708:Nucleotidases; D015720:5'-Nucleotidase; D008274:Magnesium