Purification and Molecular Properties of an Unspecific Carboxylesterase (E₁) from Rat‐Liver Microsomes

Abstract

The isolation of an unspecific carboxylesterase from rat liver microsomes is reported. The purification is 66‐fold at a yield of about 20%. The enzyme is one of 5 esterase/amidase variants recently separated and corresponds to the fraction designated E1. The enzyme is homogeneous in disc electrophoresis, dodecylsulfate‐polyacrylamide gel electrophoresis and in analytical ultracentrifugation, but exhibits slight heterogeneity in isoelectric focusing. Its amino acid composition is presented. The molecular weight of rat liver esterase E1 is 177000 (equilibrium sedimentation), the subunit weight 61 500 (dodecylsulfate disc electrophoresis), and the equivalent weight 66000 (titration with bis[p‐nitrophenyl]phosphate). After cross‐linking of the enzyme by dimethyl suberimidate and dodecylsulfate‐polyacrylamide gel electrophoresis three principal bands are observed. Therefore, a trimeric structure in which each subunit possesses one active site is proposed.

A novel carboxylesterase from Aspergillus niger and its hydrolysis of succinimide esters

“…In our case, the optimal pH for the hydrolysis of Fa-ONSu and ethyl cinnamate was found in the pH range of 5.5-7. The enzyme is a dimer with two identical subunits, each with a molecular weight of 60,000 as opposed to the carboxylesterases from mammalian liver which are trimers with three identical subunits of molecular weights of 60,000 (3,14,26).…”

“…Arylesterases preferentially cleave aromatic esters, such as esters of phenol, naphthol and indole (4). Carboxylesterases, which are rather unspecific, catalyze the hydrolysis of ester bonds, where both the alcohol moiety and the acid moiety may be aliphatic as well as aromatic (3,5,11,14,18,19).…”

“…Mammalian carboxylesterases from liver (3,11,14,15), kidney (6), pancreas (19), brain (12), and skin (23) have been studied. Those from liver are the best characterized; they are trimers consisting of three identical subunits with a molecular weight of 60,000.…”

“…Arylesterases preferentially cleave aromatic esters, such as esters of phenol, naphthol and indole (4). Carboxylesterases, which are rather unspecific, catalyze the hydrolysis of ester bonds, where both the alcohol moiety and the acid moiety may be aliphatic as well as aromatic (3,5,11,14,18,19).Carboxylesterases are involved in a number of biotransformations: hydrolysis of xenobiotic esters, activation of prodrugs, and metabolism of extraneous compounds. Some blood esterases Abbreviations: Ac = acetyl; Bz = benzoyl; Bzl = benzyl; Caps = 3-(cyclohexylamino)-l-propanesulfonic acid; Ches = 2(N-cyclohexylamino)ethane sulfonic acid; Cin = cinnamoyl; DMF = N,N-dimethylformamide; DMSO = dimethylsulfoxide; EDTA = ethylenediamine tetraacetic acid; Et = ethyl; Fa = furylacryloyl; Hepes = N-2-hydroxyethylpiperazine N'-2-ethanesulfonic acid; Hex = hexanoyl; HPLC = high performance liquid chromatography; Me = methyl; Mes = 2-(N-morpholino)ethanesulfonic acid; Ph = phenyl; PMSF = phenylmethylsulfonyl fluoride; Pr = propionyl; Oct = octanoyl; ONp = p-nitrophenoxy; ONSu = succinimidooxy; SDS = sodium dodecyl sulfate; Z = carbobenzoxy.…”

Purification and molecular properties of rabbit liver esterase ES‐1A

“…The enzymatic methylbutyrate hydrolysis was determined by the pH-stat technique [27]. Final substrate concentration was 50 mM in 10 mM Tris/HCl pH 8.0.…”