Radiation effects on rat testes. VIII. Kinetic properties of hydrolases following partial body gamma irradiation of rats.
Kinetic properties such as Michaelis constant (Km), maximum velocity (Vmax), temperature coefficient (Q10) and energy of activation (Ea) for hydrolysis of adenosine-5'-phosphate at pH 9.5 and sodium pyrophosphate at pH 8.35 by normal and radiated testes supernatants have been described. Kinetic parameters are related to respective phosphohydrolases (phosphatases). (1) Km values for 5'nucleotidase and inorganic pyrophosphatase of normal testis were determined as 1.25 X 10(-3)M and 0.81 X 10(-3)M respectively; (II) Vmax correspond to 318 mug P/15 min and 430 mug P/15 min for 100 mg tissue respectively; (III) Q10 for 5 nucleotidase is 1.7 and for inorganic pyrophosphatase is 4.2 at a temperature 10-30degreesC; (IV) Ea for hydrolysis of AMP and sodium pyrophosphate were calculated by Arrhenius plots as 17000 and 9000 cal/mol. (V) Km values for irradiated enzymes are similar to the control values suggesting that the binding capacities of these enzymes with their substrates remain unaffected after radiation; (VI) Vmax for radiated enzymes correspond to a value of 500 mug P/100 mg tissue/15 min for 5'nucleotidase and 118 mug P/100 mug tissue/15 min for inorganic pyrophosphatase; (VII) 110 for 5'nucleotidase is 2.2 and inorganic pyrophosphatase 1.16 at 10-30degreesC; (VIII) Ea for irradiated 5'nucleotidase is comparable to those of normal rats whereas for inorganic pyrophosphatase Ea is moderately declined. The observed changes have been related to the different types of metabolic activity in germinal and nongerminal cells of testes.
D000249:Adenosine Monophosphate; D000818:Animals; D011756:Diphosphates; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D009708:Nucleotidases / Q000528:radiation effects; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011755:Pyrophosphatases / Q000528:radiation effects; D011830:Radiation Effects; D011833:Radiation Injuries, Experimental / Q000201:enzymology*; D051381:Rats; D012964:Sodium; D013696:Temperature; D013737:Testis / Q000201:enzymology / Q000528:radiation effects*
D011756:Diphosphates; D000249:Adenosine Monophosphate; D012964:Sodium; D009708:Nucleotidases; D010744:Phosphoric Monoester Hydrolases; D011755:Pyrophosphatases