Immunocemical characterization of submicrosomal rat liver esterases

Abstract

Antigens from 3 submicrosomal rat liver fractions (R, Sa and Sb) were investigated for esterase activity in immunoelectrophoretic experiments with rabbit antisera against each of the subfractions. The esterases were further classified as carboxyl-, aryl-, acetyl- or choline esterases by their sensitivity to inhibition by 10 −3–10 −4 M DFP, 10 −4 M eserine, 10 −2–10 −4 M PCMB, heat and 10 M urea. The fractions R and Sa contained at least 3 acetyl esterases and 5 carboxyl esterases, while only 1 acetyl esterase and 2 carboxyl esterases were detected in the Sb-fraction. No aryl- or choline esterases were found in any of the fractions. Liver microsomes were shown to have one carboxyl esterase in common with kidney microsomes and one acetyl esterase in common with testes microsomes. By the use of different substrates, it was shown that short chain fatty acids were more easily attacked by the esterases of liver microsomes than long chain fatty acids. The activity of one esterase active antigen classified as carboxyl esterase and occurring in three variants of identical electrophoretic mobility, was strongly incresed in the R- and Sa-membranes by phenobarbital treatmet. In the Sb-membranes, this antigen is entirely missing. Two of the variants were also shown to be present in kidney microsomes where phenobarbital did not provoke any enhancement.