Arginase kinetic characterization of the ­gastropod Nacella concinna and its ­physiological relation with energy­requirement demand and the presence of heavy metals

Abstract

Arginases are metalloenzymes broadly distributed in nature. These enzymes catalyze the L-arginine hydrolyses to L-ornithine and urea. The aim of the present work is to determine the tissue levels of arginase, its kinetic properties and subcellular localization. In December 2009, specimens were collected in Admiralty Bay, King George Island near the Brazilian Research Station. The argininolytic specific activity of foot muscle, gills and pool of other tissues was 87.0 ± 15.1; 9.8 ± 1.8 and 3.8 ± 1.0 mU/mg protein, respectively. Mainly localized in the cytosol, gills and muscular arginase Km values for L-arginine were 57.0 ± 10.5 and 66.2 ± 14.6 mM, respectively. High arginase levels in gills could be related to the systemic control of L-arginine concentrations, which is vital for energetic metabolism of phospho-L-arginine and of polyamines in the control of cell proliferation though the probable physiologic metal cation is Mn 2+ , some arginases are activated by Co 2+ and Ni 2+ . The muscle Nacella concinna arginases were activated by Mn 2+ and Co 2+ and inhibited by Cd 2+ whereas; gills arginase was activated only by Mn 2+ and inhibited by Cd 2+ and Zn 2+ .