Preliminary characterisation of esterase and platelet-activating factor (PAF)-acetylhydrolase activities from cat flea ( Ctenocephalides felis) salivary glands

Abstract

Naphthyl esterase and platelet-activating factor (PAF)-acetylhydrolase activities were detected in the salivary glands of the cat flea, Ctenocephalides felis. Salivary naphthyl esterase activity is disgorged during exploratory probing. Whole extracts of salivary glands contain esterase activity against the short-chain naphthyl esters α-naphthyl acetate (∼210 pmol/min/gland pair; 10.0 μmol/min/mg specific activity; K m∼59 μM) and β-naphthyl acetate (∼110 pmol/min/gland pair; 5.2 μmol/min/mg specific activity; K m∼132 μM). Salivary gland extracts have PAF-acetylhydrolase activity (∼5 pmol/min/gland pair; 0.24 μmol/min/mg specific activity) but do not have detectable acetylcholinesterase activity. Native–PAGE and IEF resolve three and six salivary gland naphthyl esterase bands, respectively, and both patterns are different from carcass esterases. Salivary gland naphthyl esterase activity binds reversibly to Concanavalin A, and enzymatic deglycosylation with glycopeptidase F produced a new, fast-migrating salivary gland naphthyl esterase band on Native–PAGE. Renaturation of esterase activity after SDS–PAGE gave ∼56 kDa, ∼57 kDa and ∼58 kDa naphthyl-esterase-positive bands. On gel filtration naphthyl esterase and PAF-acetylhydrolase activities co-elute as a single peak with an apparent molecular weight of ∼59 kDa. This partially purified pool of enzyme had esterase activity against a series of short-chain α- and β-naphthyl esters. The heterogeneity of salivary gland esterases, their relationship to PAF-acetylhydrolase, and the possible physiological functions of salivary gland PAF-acetylhydrolase activity are discussed.