Characterization of the Esterases of Feline Serum

Abstract

Various techniques, including electrophoresis, gel filtration, titrimetric, and spectrophotometric analysis with specific and nonspecific substrates and inhibitors, were used to characterize the serum esterases of male and female cats. Starch-gel electrophoresis yielded five bands of activity: three butyrylcholinesterase bands and two bands of nonspecific carboxylesterase activity. Gel filtration on Sephadex G-200 yielded two distinct peaks of activity, one containing the cholinesterase bands and the other, the carboxylesterase activity. Kinetic characteristics determined for feline serum esterases included: (1) optimal pH; (2) optimal substrates for cholinesterase and carboxylesterase activities; (3) Km values for the choline, α-naphthyl, and p-nitrophenyl esters. With the organophosphate paraoxon as a specific substrate for arylesterase activity, low levels of this enzyme could be detected in close association with the carboxylesterase.