The relationships between human serum pseudocholinesterase, lipoproteins, and apolipoproteins (APOHDL)

During recent years there has been an increasing number of studies concerning metabolizing enzymes during lipoprotein catabolism. It is well documented that lecithin-cholesterol acyltransferase (LCAT, ED 2.3.1.43) and lipoprotein lipase (EC 3.1.1.34) take part with these reactions (1). In addition to these enzymes there has been evidence that pseudocholinesterase (EC 3.1.1.8.) is also associated with lipid metabolism (2). A relationship between serum pseudocholinesterase and low density lipoprotein (LDL) has been shown on the basis of ultrasonication studies (3) and after artifical induction of hyperlipidemia in vitro and in vivo (4). Because pseudocholinesterase activity has been previously measured only in whole serum and in DLD, our purpose has been to find out if there is any activity in other lipoprotein fractions. In addition to whole enzyme activity we investigated the distribution of pseudocholinesterase (PCE) isoenzymes in different fractions. As previously reported, LCAT and lipoprotein lipase need as cofactor, a specific apolipoprotein (5). We also studied a possible connection between HDL (high density lipoprotein) apolipoproteins (apoA-I, A-II, E, and total apoC) and PCE activity.