Human serum cholinesterase from liver pathological samples exhibit highly elevated aryl acylamidase activity

Abstract

Background Although aspartate aminotransferase (AST) and γ-glutamyltransferase (γGT) enzymes are widely used as markers for liver disorders, the ubiquitous enzyme butyrylcholinesterase (BChE), synthesized in liver is also used as marker in the assessment of liver pathophysiology. This BChE enzyme in addition to its esterase activity has yet another enzymatic function designated as aryl acylamidase (AAA) activity. It is determined in in vitro based on the hydrolysis of the synthetic substrate o-nitroacetanilide. In the present study, human serum cholinesterase (BChE) activity was studied with respect to its AAA activity on the BChE protein (AAA BChE) in patients with liver disorders. AST and γGT values were taken into account in this study as known markers for liver disorders. Methods Blood samples were grouped into 3 based on esterase activity associated with BChE protein. They are normal, low, and very low BChE activity but with markedly increased AST and γGT levels. These samples were tested for their respective AAA function. Association of AAA with BChE from samples was proved using BChE monoclonal antibody precipitation experiment. Results The absolute levels of AAA were increased as BChE activity decreased while deviating from normal samples and such deviation was directly proportional to the severity of the liver disorder. Differences between these groups became prominent after determining the ratios of AAA BChE to BChE activities. Samples showing very high AAA BChE to BChE ratio were also showing high to very high γGT values. Conclusions These findings establish AAA BChE as an independently regulated enzymatic activity on BChE especially in liver disorders. Moreover, since neither the low esterase activity of BChE by itself nor increased levels of AST/γGT are sufficient pathological indicators, this pilot study merits replication with large sample numbers.