Physico-chemical properties of hepatocyte plasma-membrane-bound arginase.
Rat liver plasma-membrane-bound arginase was investigated in order to obtain data regarding its physico-chemical properties. Arginase bound to plasma membrane presented a specific activity of 0.74 +/- 0.09 IU/mg for the fully-activated enzyme, the pH of maximum activity being 9.8. Maximum stability was recorded at two pH values, 7 and 10.5 respectively. Mn2+ activated the enzyme, while Cu2+ and Zn2+, and to a lesser extend Co2+, showed a strong inhibitory effect. Ca2+ and Mg2+ had no effect at the concentrations assayed. The influence of temperature was studied in the presence and in the absence of Mn2+. The enzyme was stable up to 65 degrees C in both cases. Membrane- bound arginase showed an activation energy of 11.5 +/- 1.4 Kcal/mol between 20 and 40 degrees C, and 13.3 +/- 2.5 Kcal/mol between 40 and 60 degrees C. The Q10 for the same temperature ranges were 1.78 and 1.9 respectively. The membrane-bound enzyme presented two different Michaelis constants, one with high affinity (2.05 +/- 0.73 mM) and the other with low affinity for arginine (130 +/- 27.2 mM). Solubilized arginase showed very similar values. Among all the structural analogous assayed, only L-canavanine proved to be substrate for arginase, with and L-arginine/L-canavanine hydrolysis ratio of 5.8 +/- 0.28. No reactivity was found between plasma-membrane-bound arginase and anti-rat liver arginase antibodies raised in rabbits.
Fuentes
J M
JM
Department of Biochemistry, Molecular Biology and Genetics, University of Extremadura, Faculty of Veterinary Sciences, Cáceres, Spain.
Campo
M L
ML
Soler
G
G
D000818:Animals; D001119:Arginase / Q000737:chemistry*; D002413:Cations, Divalent; D002462:Cell Membrane / Q000201:enzymology; D003429:Cross Reactions / Q000276:immunology; D004795:Enzyme Stability / Q000502:physiology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry*; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D002413:Cations, Divalent; D007527:Isoenzymes; D001119:Arginase