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 R₁ is hydrogen or methyl, and R₂ is C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₂-C₁₀ alkynyl, C₁-C₄ haloalkyl, a C₅-C₉ aliphatic hydrocarbon moiety which may be optionally protected on the terminal hydroxyl group thereof, or a C₅-C₉ 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.