In situ evaluation of esterase stereoselectivity in two-dimensional electropherograms and tissue sections

Abstract

Staining with both enantiomers of an α-naphthyl ester plus a diazonium salt and comparing the color intensities given by the two enantiomers is a convenient method to evaluate the esterase stereoselectivity for that ester in two-dimensional electropherograms and tissue sections. Application of this method for rat liver has shown that (1) several esterases, e.g., one of p I 6.4 and M r 118 kDa, are moderately stereoselective against α-naphthyl ( R)- N-acetylalaninate and ( R)- N-methoxycarbonylalaninate but strictly stereoselective against α-naphthyl ( S)- N-methoxycarbonylvalinate, implying that esterase stereoselectivity may be inverted by changing the ester structure; and (2) these esterases are mainly contained in the hepatocytes around central veins.