Esterase Studies on Dog Mast-cell Tumours

Abstract

RECENTLY our laboratory reported the isolation of proteolytic enzymes from a dog mast-cell tumour using DEAE-cellulose and CM-cellulose columns. An esterase which split N-acetyltyrosine ethyl ester (ATEe) and another which split p-toluene sulphonyl-l-arginine methyl ester (TAMe) were described¹. Using column chromatography and eluting with a concentration gradient of phosphate buffer with a pH of 8.0, several peaks of ATEe esterase and two TAMe esterase peaks were found. All the peaks of ATEe esterase have since been found to have a similar Michaelis constant (Km) of 1.0–1.5 mM, except one which had a Km value of about 4 mM. From these observations the different peaks of ATEe esterase with similar Km values were postulated to be one enzyme.