P-NITROPHENYLACETATE HYDROLYSIS BY HONEY-BEE ESTERASES - KINETICS ANDINHIBITION

1. The kinetics and inhibition of p-nitrophenylacetate hydrolysis by c ytosolic esterases of 1-day old female honey bees, Apis mellifera L., were studied. 2. The calculated values obtained were K(m) = 2.27 x 10( -5) M and V(max) = 2.48 x 10(-8) mol/s per mg protein. 3. The inhibiti on mechanisms examined for four organophosphorus insecticides were hig hly competitive in nature and based on competitive inhibition coeffici ents the order of toxicity was naled > dichlorvos > cis-mevinphos = tr ans-mevinphos. 4. Comparisons are made with the alfalfa leafcutting be e, Megachile rotundata (Fab).