Esterase

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

Studies on human c'1-esterase. i. purification and enzymatic properties.

Abstract: Summary C′1-esterase was isolated by column chromatography on DEAE and TEAE cellulose of a euglobulin fraction of human serum. The final product, purified 2400-fold with respect to serum, contained 3800 enzyme units/mg of nitrogen, as measured by zero-order hydrolysis of N-acetyl-L-tyrosine ethyl ester (ATE). The purified preparation migrated as an α 2 -globulin on paper electrophoresis but was heterogeneous in the analytical ultracentrifuge. The susceptibility to hydrolysis of synthetic substrates, listed in decreasing order of activity, was: N-acetyl-L-tyrosine ethyl ester, N-acetyl-L-tyrosine methyl ester, benzoyl-L-arginine ethyl ester, p -toluenesulfonyl-L-arginine methyl ester, and N-acetyl-L-phenylalanine ethyl ester. Nonsusceptible substrates included L-lysine methyl ester. Maximal hydrolysis of ATE occurred at a final concentration of substrate of 5 × 10 -2 M (K m = 1.9 × 10 -2 M), pH 6.7 to 8.0, ionic strength below 0.20, and 38.8°C (apparent energy of activation = 10,400 calories/mole). No dependency of esterolytic activity on divalent cations was demonstrable. These properties are similar to those of previous preparations of human and guinea pig C′1-esterase obtained either from less purified fractions of serum or from elution of antigen-antibody-complement complexes. Possible explanations for the observed physicochemical heterogeneity are discussed. The function of this highly purified preparation of human C′1-esterase in the complement system is presented in the following article.

Influence of different xylanases on the activity of ferulic acid esterase on wheat bran

Abstract: The apparent specific activity of ferulic acid esterases on cell wall polysaccharide materials is enhanced by the presence of xylanases. In this paper we show that the extent of the synergy between an Aspergillus niger ferulic acid esterase (FAE-III) and various xylanases [β-(1,4)-D-xylan xylanohydrolases (EC 3.2.1.8)] in releasing ferulic acid from de-starched wheat bran is strongly dependent on the source of the xylanase. Differences among the xylanases are found to be due to (a) the rate of hydrolysis of wheat bran cell wall polysaccharides and (b) the size distribution and nature of the products solubilized in the hydrolysis. In addition, analysis of the low-molecular-mass carbohydrate products indicates that the initial rate of the hydrolysis by the xylanase is also enhanced by the addition of the esterase, showing a reciprocal co-operation between the enzymes.

The gene for albicidin detoxification from Pantoea dispersa encodes an esterase and attenuates pathogenicity of Xanthomonas albilineans to sugarcane

Abstract: Albicidin phytotoxins are pathogenicity factors in a devastating disease of sugarcane known as leaf scald, caused by Xanthomonas albilineans. A gene (albD) from Pantoea dispersa has been cloned and sequenced and been shown to code for a peptide of 235 amino acids that detoxifies albicidin. The gene shows no significant homology at the DNA or protein level to any known sequence, but the gene product contains a GxSxG motif that is conserved in serine hydrolases. The AlbD protein, purified to homogeneity by means of a glutathione S-transferase gene fusion system, showed strong esterase activity on p-nitrophenyl butyrate and released hydrophilic products during detoxification of albicidins. AlbD hydrolysis of p-nitrophenyl butyrate and detoxification of albicidins required no complex cofactors. Both processes were strongly inhibited by phenylmethylsulfonyl fluoride, a serine enzyme inhibitor. These data strongly suggest that AlbD is an albicidin hydrolase. The enzyme detoxifies albicidins efficiently over a pH range from 5.8 to 8.0, with a broad temperature optimum from 15 to 35°C. Expression of albD in transformed X. albilineans strains abolished the capacity to release albicidin toxins and to incite disease symptoms in sugarcane. The gene is a promising candidate for transfer into sugarcane to confer a form of disease resistance.

Coamplification of esterase A and B genes as a single unit in Culex pipiens mosquitoes.

Abstract: In Culex pipiens mosquitoes, resistance to organophosphorous insecticides often results from increased detoxification by two types of esterases, A and B, which are closely linked. Overproduction of all esterase B so far investigated (B1, B2, B4, B5 and B6) is from gene amplification. An esterase A gene (esterase A2) has recently been cloned from mosquitoes with the overproduced esterases A2 and B2, and amplification of this gene has also been reported. We describe the cDNA sequences of three additional esterase genes from insecticide-resistant strains of Culex pipiens originating from France and California which show at least 93 per cent homology with the esterase A2 gene sequence. Restriction enzyme mapping shows that the esterase A gene lies within 2.2 kb of the esterase B gene. In mosquitoes with overproduced esterases A2 and B2, the amplification level of esterase A is equal to that of esterase B suggesting that the genes are coamplified. Furthermore, we show that in one strain with an overproduced A esterase (A1), gene amplification cannot account for the increased protein level. This indicates that overproduction of esterases A can be achieved through two different mechanisms: gene amplification and a regulatory mechanism--the nature of which remains to be identified.