ESTERASE-30 (ES-30) OF THE HOUSE MOUSE - BIOCHEMICAL-CHARACTERIZATIONAND GENETICS OF A NEW CARBOXYLESTERASE ISOZYME LINKED TO CLUSTER-2 LOCI ON CHROMOSOME 8

A new carboxylesterase isozyme (EC 3.1.1.1), designated ES-30, is desc ribed in mouse liver. Two phenotypes were distinguished, ES-30A, a pos sible null type, was found in SPE/Pas and in other lines derived from Mus spretus, and ES-30B was found in BALB/cJ and other laboratory inbr ed strains. ES-30B is characterized by a distinct electrophoretic band when stained using 5-bromoindoxyl acetate as the substrate. After iso lation and purification from other esterases by ion-exchange chromatog raphy and molecular sieving, the molecular mass was estimated by two i ndependent methods to be 62 and 64 kDa, respectively. The activity of ES-30B is higher in adult males than in females and can be stimulated in vivo by testosterone. The distribution of phenotypes on the progeny of a backcross series suggests a separate locus, Es-30, with the alle le a for absence and b for presence of the isozyme. Locus Es-30 is sho wn to be closely linked to Es-2 and to Es-7 of cluster-2 on chromosome 8. The gene order Es-9-Got-2-(Es-2, Es-7, Es-30) is suggested.