An isolated esterase gene coding for an esterase capable of causing asymmetric hydrolysis of an organic carboxylic acid ester of a cyclopentenolone of formula I: ##STR1## wherein R.sub.1 is hydrogen or methyl, and R.sub.2 is C.sub.1 -C.sub.10 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.10 alkynyl, C.sub.1 -C.sub.4 haloalkyl, a C.sub.5 -C.sub.9 aliphatic hydrocarbon moiety which may be optionally protected on the terminal hydroxyl group thereof, or a C.sub.5 -C.sub.9 fatty acid residue which may be optionally protected on the terminal carboxyl group thereof, to produce the cyclopentenolone of formula I in (R)-form, and hybridizing to the base sequence of SEQ ID NO:1, is useful for the industrially favorable production of optically active cyclopentenolones of formula I which serve as the intermediates of drugs, agricultural chemicals or other active products.