Characterization of the esterases of the mitochondrial fraction of guinea pig cortical renal cells.

The esterase activity of the mitochondrial fraction from cortical renal cells was studied in guinea pigs aged 15, 21, 30, and 120 days. The rate of hydrolysis of beta-naphthyl acetate was measured by incubating aliquots of mitochondrial preparations with physostigmine, diisopropylfluorophosphate, HgCl2, and p-hydroxymercuribenzoate. Enzyme activity was mainly due to the heterogeneous aliesterase group: some aliesterases were sensitive to physostigmine, others to organophosphorus compounds and/or to HgCl2; a C-esterase stimulated by organomercurials and similar to that described by Bergmann et al. in hog kidney was detected (F Bergmann, R Segal, S Rimon. Biochem J 67:481-486, 1957); arylesterase activity was very weak. Acetylthiocholine used as substrate showed there was no cholinesterase activity in the mitochondrial fraction.