STRUCTURAL DIFFERENCE AT ACTIVE-SITE OF DIBUCAINE RESISTANT VARIANT OF HUMAN-PLASMA CHOLINESTERASE

Abstract

Human plasma cholinesterase from 5 different genotypes.sbd.E1UE1U, E1UE1a, E1aE1a, E1UE1s, E1aE1s and E1UE1U C5[complement component 5] +.sbd.was purified 8000-fold from serum by a 2-step procedure involving chromatography on DEAE-cellulose and preparative disc electrophoresis. The esterases were labeled with diisopropyl-1. 3-C14-fluorophosphate (DFP), aminoethylated, and digested by trypsin. The tryptic digests were subjected to high voltage electrophoresis, and the radioactive peptides were detected by radioautography. Comparison of the peptides revealed different electrophoretic mobilities of the usual and atypical (dibucaine resistant) plasma cholinesterase peptides. The results are consistent with a structural abnormality of the active center in the variant enzyme. No difference was observed at the esteratic site of the enzyme with C5 component.