First report of carnitine palmitoyltransferase-I activity in crustaceans

LAVARIAS S,; PASQUEVICHY,; DREON MS,; POLLERO RJ,; HORACIO HERAS

Rosario

Congreso; XLII Reunión conjunta SAIByBM y Soc. Argentina de Neurociencias (SAN); 2006

Carnitine palmitoyltransferase-I (CPT-I) is a key enzyme in the control of long-chain fatty acid oxidation that catalyzes the conversion of acyl-CoA to acylcarnitine in the outer mitochondrial membrane. In a previous work, we reported an increase in fatty acid activation and b-oxidation in mitochondria of the hepatopancreas of the freshwater prawn Macrobrachium borellii after a chronic exposure to water soluble fraction (WSF). The aim of this work was to characterize its CPT-I enzymatic activity as a follow up on the research on the effect of the WSF exposure on lipid metabolism. CPT-I activity was assayed by measuring the release of CoA-SH spectrophotometrically (Ellman’s reaction) using palmitoil-CoA and L-carnitine as substrates. We observed a linear relationship between the mitochondrial protein and the enzyme activity up to 67 µg/ml. A great temperature dependence was observed with an optimum value at 34°C; the optimum pH value for this prawn CPT I was 8.0. The Hill coefficient, n ≈1 using palmitoil-CoA, indicates a Michaelis-Menten behavior. The kinetics parameters, Km and Vmax were 259.6 mmol.l-1, and 76.8 nmol. min-1. mg protein-1, respectively. Finally, after 7 days exposure to a sublethal concentration of WSF (0.6 mg/l), an increasing trend of CPT-1 activity was observed between control and exposed shrimps. This is the first report of CPT-1 activity in crustaceans.