Activity and Subcellular Distribution of Phosphatidate Phosphohydrolase (Ec 3.1.3.4) in Alcoholic Liver Disease

A micromethod was developed to assay the hepatic activity and subcellular distribution of phosphatidate phosphohydrolase (PAH, EC 3.1.3.4), an important regulatory enzyme in triacylglycerol synthesis, in human needle biopsy specimens. In normal liver PAH is predominantly cytosolic in distribution, but on treatment with oleic acid it shifts to the membranous compartments of the cell, its physiologically active site. The hepatic specific activity of PAH was similar in controls and patients with fatty liver but significantly more of the enzyme was associated with the membranous compartments in patients with severe alcoholic fatty liver. These observations may explain the enhanced rates of triacylglycerol synthesis observed in these patients and may be implicated in the pathogenesis of alcoholic fatty liver.