Purification and characterization of human heart fatty acid ethyl ester synthase/carboxylesterase

Fatty acid ethyl ester synthase metabolizes ethanol non-oxidatively in those extrahepatic organs most commonly damaged by alcohol abuse. This study was designed to purify human myocardial fatty acid ethyl ester synthase (FAEES)/carboxylesterase from human heart. The enzyme was purified to homogeneity after chromatography over DEAE-cellulose, Sephadex G-100 and hydroxylapatite. The homogenous enzyme, 62 kDa, has both synthase and carboxylesterase activities. The N-terminal amino acid sequence of the first 17 residues of the purified enzymes were 88% homologous to that of the carboxylesterase from rat liver and adipose tissue. Antibody was raised against pure synthase/carboxylesterase cross-reacted with human cytosolic and microsomal fractions. With a constant oleic acid concentration of 0.25 mM, a calculated apparent Km and Vmax for ethanol were 0.30 M and 3700 nmol/mg protein/h., respectively. With constant ethanol concentrations of 1.2 M, the activity increased with the concentration of oleic acid to 0.17 mM, plateau to 0.25 mM. Because synthase/carboxylesterase esterifies free fatty acids with ethanol to produce its esters with potentially toxic effects, it may now be feasible to establish a link between alcohol consumption and end-organ damage.