Human red cell butyrylesterase, and its homologies in thirteen other mammalian species.

The selective staining of a single butyrylesterase, following isoelectric focusing of red cell lysates from 14 mammalian species, including man, was achieved using the chromogenic substrate N-acetyl-L-alanine-alpha-naphthyl ester. This procedure optimized the identification of this enzyme, and a close correspondence of its properties was observed in all the species investigated. The inhibition profile, using a range of inhibitors, was identical in all cases. Particularly noteworthy was the activation of the enzyme by p-chloromercuribenzoate at low (2-20 x 10(-6) M) concentrations, but inhibition at higher (greater than 10(-3) M) concentrations. The isoelectric points of all samples fell within a narrow range, pI 4.00-4.43. Descriptions of this activity in different animals, under different designations, could be identified in earlier studies, and the enzyme was uniformly designated "butyrylesterase 1". A tetrameric subunit structure, previously established for the human enzyme, was also demonstrated in the case of mouse butyrylesterase 1. A list of diagnostic characteristics for the enzyme was presented, and it was assumed that the 14 enzymes investigated are orthologous. It was not possible to group butyrylesterase 1 with any other known esterase within the system of enzymes recommended by the IUB, and it was proposed that this enzyme be assigned to a new esterase subclass.