Esterase

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

Characteristics of the genetically determined allozymic forms of human serum paraoxonase/arylesterase.

Abstract: Human serum paraoxonase/arylesterase is an esterase with broad substrate specificity. It occurs in two genetically determined allozymic forms, which we have designated types A and B. These allozymes are presumed to be the products of two allelic genes located at the paraoxonase locus on chromosome 7, which is closely linked to the gene for cystic fibrosis. Paraoxonase activity of the B-type isozyme is considerably higher and stimulated more by 1 M NaCl than A-type paraoxonase. The ratio of paraoxonase activity/arylesterase activity of the B-isozyme is about 8, and that of the A-isozyme about 1. Purified isozymes A or B are free of nearly all other serum proteins, and the broad substrate specificity of the serum esterase is preserved after purification. A variety of substrates are hydrolyzed; these include: diisopropylfluorophosphate, soman, sarin, 4-nitro-phenylacetate, 2-nitro-phenylacetate, 2-naphthylacetate, and phenylthioacetate. The isozymic distinctions in kinetic properties and substrate specificity are preserved during purification. It is likely that the allozymes have very similar turnover numbers with phenylacetate (arylesterase activity), but differ considerably in their turnover numbers with paraoxon. Isozymes A and B have about the same minimal molecular weight of 43,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Further detailed studies on the individual isozymic proteins (or the DNA coding for their amino acid sequence) will be required to detect the exact structural differences in the isozymes.

Male esterase 6 catalyzes the synthesis of a sex pheromone in Drosophila melanogaster females

Abstract: Esterase 6, a component of the seminal fluid of Drosophila melanogaster males, hydrolyzes cis-vaccenyl acetate, a lipid made only by males, to cis-vaccenyl alcohol. This reaction occurs in the female reproductive tract and is virtually complete within 6 hours after copulation. Both the alcohol and the acetate decrease the number of matings among pairs of virgin flies in which the female is treated topically with these substances. Although females tested 10 minutes after copulation elicit less courtship than virgin females, females tested 6 hours after copulation stimulate even less courtship if they received active esterase 6 in the seminal fluid of their respective mates. Either the alcohol or a derivative appears to be an antiaphrodisiac that decreases courtship elicited by inseminated females and thus reduces the probability of further mating. Thus the activity of the pheromone depends on a final reaction which occurs in the female, using both substrate and enzyme provided by the male.

Discrimination of B, T and null lymphocytes by esterase cytochemistry.

Abstract: A technique has been devised which optimally demonstrates non-specific esterase activity in human blood lymphocytes. The reaction is carried out on smears fixed with formalin vapour, using alpha-naphthol butyrate as substrate at pH 8 and at a low concentration for a short incubation period. The pattern of esterase activity revealed by this method provides a discriminating marker for mature T-lymphocytes, which show dense, localised, dot-like positivity, and a probable marker for 'null' cells in the form of scattered granular positivity. B cells appear to be negative. Monocytes show a clearly different pattern of granular positivity.

Purification and Characterization of a Feruloyl Esterase from the Intestinal Bacterium Lactobacillus acidophilus

Abstract: Dietary ferulic acid (FA), a significant antioxidant substance, is currently the subject of extensive research. FA in cereals exists mainly as feruloylated sugar ester. To release FA from food matrices, it is necessary to cleave ester cross-linking by feruloyl esterase (FAE) (hydroxycinnamoyl esterase; EC 3.1.1.73). In the present study, the FAE from a human typical intestinal bacterium, Lactobacillus acidophilus, was isolated, purified, and characterized for the first time. The enzyme was purified in successive steps including hydrophobic interaction chromatography and anion-exchange chromatography. The purified FAE appeared as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular mass of 36 kDa. It has optimum pH and temperature characteristics (5.6 and 37 degrees C, respectively). The metal ions Cu(2+) and Fe(3+) (at a concentration of 5 mmol liter(-1)) inhibited FAE activity by 97.25 and 94.80%, respectively. Under optimum pH and temperature with 5-O-feruloyl-L-arabinofuranose (FAA) as a substrate, the enzyme exhibited a K(m) of 0.0953 mmol liter(-1) and a V(max) of 86.27 mmol liter(-1) min(-1) mg(-1) of protein. Furthermore, the N-terminal amino acid sequence of the purified FAE was found to be A R V E K P R K V I L V G D G A V G S T. The FAE released FA from O-(5-O-feruloyl-alpha-L-arabinofuranosyl)-(1-->3)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose (FAXX) and FAA obtained from refined corn bran. Moreover, it released two times more FA from FAXX in the presence of added xylanase.