“PRESENCE OF CARNITINE PALMITOYLTRANSFERASE I ACTIVITY IN THE HEPATOPANCREAS OF Macrobrachium borellii”

LAVARIAS, SABRINA MARÍA LUISA; PASQUEVICH, Y.; DREON, M.; POLLERO, R.; HERAS, H.

Coquimbo, Chile.

Congreso; Mid-Year Meeting, The Crustacean Society; 2007

The Crustacean Society

Carnitine palmitoyltransferase-I (CPT-I) catalyzes the conversion of acyl-CoA to acylcarnitine at the outer mitochondrial membrane and is a key enzyme in the control of long-chain fatty acid oxidation. In a previous work, we reported the activities of the activation and b-oxidation of palmitic acid in hepatopancreas mitochondrias of the freshwater crustacean M. borellii, two of the key pathways of the fatty acid catabolism. The aim of this work was to characterize the CPT I enzymatic activity in this species. Activity was assayed using palmitoyl-CoA and L-carnitine as substrates and following the release of  CoA-SH spectrophotometrically by the Ellman reactive reaction. We observed a linear relationship between the mitochondrial protein and the enzyme activity up to 66.7 µg/ml. A large temperature dependence was observed with an optimum value at 34°C, and the optimum pH value for CPT I was 8.0. The Hill coefficient, was approximately 1 using palmitoyl-CoA, indicating a Michaelis-Menten behavior. The kinetic parameters, Km and Vmax were 92.2 µmol.l-1, and 16 nmol. min-1. mg protein-1, respectively. When the L-carnitine was studied as substrate the kinetic parameters, Km and Vmax were 2.181 mmol.l-1, and 30.2 nmol. min-1. mg protein-1, respectively. The effect of vertebrate mitochondria inhibitors such as Malonyl-CoA was also studied. This is the first report about the presence of CPT I in crustaceans which appears to have lower affinity but higher Vmax for the substrate than  CPT I  from other taxa.