Purification and characterization of a novel 46.5-kilodalton esterase from mouse hepatic microsomes.

A novel membrane-bound esterase was purified from mouse hepatic microsomes. The purified protein (ES46.5K) showed a single protein-staining band on sodium dodecyl sulfate-polyacrylamide gel with a minimum molecular weight of 46.5 Kdalton. ES46.5K possessed esterase activity toward 11-acetoxy-delta 8-tetrahydrocannabinol (11-OAc-delta 8-THC) (27.1 mumol/min/mg protein) and p-nitrophenylacetate (119 mumol/min/mg protein), and these activities were 38 and 47 times, respectively, as high as those of microsomes. The N-terminal amino acid sequence of the protein was as follows: G-K-T-I-S-L-L-I-S-V-V-L-V-A-Y-Y-L-Y-I. This sequence has no homology to those of the known carboxylesterases, indicating that this enzyme is a novel type of esterase bound to the microsomal membrane.