Partial characterization of alanine aminotransferase from gills and digestive gland of the bivalve Ruditapes philippinarum

11 páginas, 12 figuras, 3 tablas.

The activity of alanine aminotransferase (AIAT) from the gills and digestive gland of Ruditapes philippinarum was measured in the direction of pyruvate formation. Kinetic and physiocochemical properties, including the effects of inorganic ions, amino acids, organic acids, nucleotides and some heavy metals on enzyme action, were investigated. The optimal pH for AIAT activity in tissue from both sources was between 6.0 and 7.5. The apparent Km values for alanine and 2-oxoglutarate decreased as pH increased in the gill enzyme, but no appreciable variation was observed with the digestive gland enzyme. The activation energies of the gill and digestive gland enzymes were similar, with values of 10.0 ± 0.3 and 8.2 ±0.3 kcal mol1, respectively and Q10 values of 1.54 and 1.33, respectively. The electrophoretic analysis showed two bands for gills and only one in digestive gland. The dicarboxylic acids phthalate and glutarate had an inhibitory effect on AIAT activity, as did the heavy metals Hg2+, Cd2+, Pb2+ and Zn2+. The kinetic analysis suggested that these heavy metals combine with both the pyridoxal and pyridoxalamine forms of the enzyme, interacting in different ways with several groups within the enzyme.

J. Puppo was recipient of a fellowship from the Plan Nacional Formación Personal Investigador, MEC, Spain.

Peer reviewed