Serum esterase genetics: identification and hormone induction of the Es-1b esterase in inbred rats

A previously unrecognized esterase from the sera of the appropriate strains of the rat Rattus norvegicus was revealed by a discontinuous polyacrylamide gel electrophoretic technique. This esterase migrated in the albumin region, whereas a previously known major albumin esterase controlled by the Es-2 locus migrated in the postalbumin region when the method was used. The new albumin esterase component which separated from the Es-2 esterase was identified as the product of the Es-1b gene. The new albumin esterase was not detectable in the sera of sexually mature males of the appropriate genotype, because the activity level of this esterase was influenced by sex hormones, especially androgen.