Direct evaluation of stereoselectivity of cancer esterases by polyacrylamide gel electrophoresis coupled with activity staining with chiral naphthyl esters.

Both enantiomers of alpha-naphthyl 2-phenylpropanoate (PhPr(ONap)), N-acetylalaninate (AcAla(ONap)), N-methoxycarbonylalaninate (MocAla(ONap)), N-methoxycarbonylvalinate (MocVal(ONap)), N-acetylprolinate (AcPro(ONap)), and N-(trifluoroacetyl)prolinate (TfaPro(ONap)) were prepared and used with Fast Blue RR salt for activity staining of esterases separated by polyacrylamide gel electrophoresis. Comparison of the band thicknesses stained with each enantiomer indicates stereoselectivity of the major esterase in that band. Several esterases in normal rat liver, rat hepatoma-derived cells, and mouse B16 melanoma showed alteration or inversion of stereoselectivity by the substrate change from MocAla(ONap) to MocVal(ONap) or from AcPro(ONap) to TfaPro(ONap). The stereoselectivity of the major esterases for MocVal(ONap) was reversed between the murine liver and the B16 melanoma enzymes. The present staining with chiral naphthyl esters is very effective for surveying rapidly the stereoselectivity of animal tissue and cancer esterases.