Localização Subcelular e Propriedades Cinéticas da Arginase Hepática da Raia Zapteryx brevirostris (Müller e Henle, 1841) (Elasmobranchii, Rhinobatidae)

Resumo

The argininolytic activity of the liver of Zapterix brevirostris was studied at a pH and temperature close to the physiological conditions using preparation of arginase in mitochondrial suspension and partial purification. The kinetic behavior is characteristic of enzymes with two active sites. For arginase in mitochondrial suspension, Kmapp1 = 1,22±0,17 mM and Kmapp2 = 64,29±14,77 mM, and for partial purified arginase with Km1 = 2,32±0,17 mM and Km2 = 561,50±899,40 mM were obtained. The manganese cation in concentrations up to 0.25 mM has an activation effect on the arginase activity and an inhibitory effect with concentrations above 0.5 mM in both preparations. For arginase in mitochondrial suspension and in partial purification, the values of IC50 for MnCl2 were 4.16 mM and 3.07 mM respectively. The studies indicate that the mitochondrial membranes are the probable sites that control the Larginine metabolism.