An ATP-inhibited soluble 5'-nucleotidase of rat kidney.
Hydrolysis of 5'-AMP by 5'-nucleotidase is a possible source of adenosine in the kidney. A renal membrane-bound ecto-5'-nucleotidase has been previously described. The present study deals with the catalytic properties of a 5'-AMP phosphohydrolase partially purified from high-speed supernatants of rat kidney homogenates. It exhibits phosphatase activity toward 5'-AMP, 5'-IMP, and 5'-GMP, but not toward 2'- and 3'-AMP and corresponds therefore to a 5'-nucleotidase. The hydrolysis of 5'-AMP by the soluble 5'-nucleotidase requires divalent cations. Maximal activity is reached with 10 microM of either Mn2+ or Co2+, whereas half-maximal activity is obtained with approximately 400 microM Mg2+. The soluble 5'-nucleotidase exhibits Michaelis-Menten kinetics with a Km of 9.5 microM for 5'-AMP. In the presence of 1 mM of free Mg2+, physiological concentrations of ATP provoke an increase of the Km for 5'-AMP and a decrease of Vmax. An increase of the pH of 0.4 units in the pH range 6.4-7.4 roughly doubles the rate of hydrolysis of 5'-AMP. The effects of ATP and of the pH are compatible with a role of the renal soluble 5'-nucleotidase in the hydrolysis of 5'-AMP and in the production of adenosine during hypoxia.
Le Hir
M
M
Medizinische-Universitaetspoliklinik, Kantonspital, Basel, Switzerland.
Dubach
U C
UC
D015720:5'-Nucleotidase; D000241:Adenosine / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002413:Cations, Divalent / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000201:enzymology*; D008297:Male; D009708:Nucleotidases / Q000037:antagonists & inhibitors*; D010710:Phosphates / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D002413:Cations, Divalent; D010710:Phosphates; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate; D009708:Nucleotidases; D015720:5'-Nucleotidase; D000241:Adenosine