Human serum pseudocholinesterases: molecular weight estimation of a subunit structure.

Abstract

Molecular weight determinations by gel filtration on Sephadex G-200 were performed on fractions of human serum cholinesterases as obtained after ultrafiltration through a semipermeable membrane. The molecular weight of the fraction filtering through a membrane with molecular weight exclusion limits of 100 000 was estimated to be 86 000, whereas that of the fraction retained by the filter was higher than 300 000, approximating the value of 348 000 previously reported in the literature. Both fractions were shown to be interconvertible under the experimental conditions used. These results provide further evidence in favor of the existence of an enzymatically active subunit structure of cholinesterases and suggest that subunits combine into tetramers to form the major component of the cholinesterase activity in human serum.