Esterase

About: Esterase is a research topic. Over the lifetime, 7622 publications have been published within this topic receiving 168270 citations.

EstB from Burkholderia gladioli: a novel esterase with a beta-lactamase fold reveals steric factors to discriminate between esterolytic and beta-lactam cleaving activity

Abstract: Esterases form a diverse class of enzymes of largely unknown physiological role. Because many drugs and pesticides carry ester functions, the hydrolysis of such compounds forms at least one potential biological function. Carboxylesterases catalyze the hydrolysis of short chain aliphatic and aromatic carboxylic ester compounds. Esterases, D-alanyl-D-alanine-peptidases (DD-peptidases) and beta-lactamases can be grouped into two distinct classes of hydrolases with different folds and topologically unrelated catalytic residues, the one class comprising of esterases, the other one of beta-lactamases and DD-peptidases. The chemical reactivities of esters and beta-lactams towards hydrolysis are quite similar, which raises the question of which factors prevent esterases from displaying beta-lactamase activity and vice versa. Here we describe the crystal structure of EstB, an esterase isolated from Burkholderia gladioli. It shows the protein to belong to a novel class of esterases with homology to Penicillin binding proteins, notably DD-peptidase and class C beta-lactamases. Site-directed mutagenesis and the crystal structure of the complex with diisopropyl-fluorophosphate suggest Ser75 within the "beta-lactamase" Ser-x-x-Lys motif to act as catalytic nucleophile. Despite its structural homology to beta-lactamases, EstB shows no beta-lactamase activity. Although the nature and arrangement of active-site residues is very similar between EstB and homologous beta-lactamases, there are considerable differences in the shape of the active site tunnel. Modeling studies suggest steric factors to account for the enzyme's selectivity for ester hydrolysis versus beta-lactam cleavage.

Cytological and cytochemical studies on cell death and digestion in the foetal rat foot: the role of macrophages and hydrolytic enzymes.

Abstract: Physiological cell death and degeneration in the interdigital mesenchyme of the hind foot of the rat foetus have been studied using classical staining methods and staining methods for enzyme localization. Individual mesenchymal cells die and shrink as the result of some unknown mechanism. Their acid phosphatase and esterase activities are not significantly different from those of viable loose mesenchymal cells. The dead cells are engulfed by viable neighbouring cells which resemble other loose mesenchymal cells in their morphology and in their acid phosphatase and esterase activities. These phagocytes then differentiate and become typical macrophages. Expressions of this process are the altered appearance of their nuclei and the increase in cytoplasm and in acid phosphatase and esterase activities. Many dead cells may be engulfed by a single macrophage and are then digested by its acid hydrolases. No evidence was found suggesting that cell death might be initiated by the intracellular release of lysosomal enzymes.

Mechanisms of activation of C'1 esterase in hereditary angioneurotic edema plasma in vitro.

Abstract: The generation of C'1 esterase activity in siliconed plasma obtained from individuals with hereditary angioneurotic edema in remission tends to occur spontaneously, but can be hastened during its incubation with preparations of activated Hageman factor. This effect of activated Hageman factor could not be shown during its incubation with normal siliconed plasma, nor could consumption of normal serum inhibition of C'1 esterase be clearly shown. Soy bean trypsin inhibitor and heparin could impair this enhanced generation of C'1 esterase but neither inhibits the esterolytic function of C'1 esterase once formed. Trasylol was less effective in blocking this effect of activated Hageman factor. While the mechanism of the effect of activated Hageman factor upon C'1 activation remains obscure, it is apparent that some intermediate steps, possibly involving a kinin-forming system of plasma, may play a role.