Esterase

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

Enzymatic Production of l-Menthol by a High Substrate Concentration Tolerable Esterase from Newly Isolated Bacillus subtilis ECU0554

Abstract: Enzymatic preparation of l-menthol has been attracting much attention in the flavor and fragrance industry. A new ideal strain, Bacillus subtilis ECU0554, which exhibited high hydrolytic activity and excellent enantioselectivity towards l-menthyl ester, has been successfully isolated from soil samples through enrichment culture and identified as Bacillus subtilis by 16S rDNA gene sequencing. The esterase extracted from B. subtilis ECU0554 (BSE) showed the best catalytic properties (E > 200) for dl-menthyl acetate among the five menthyl esters examined. Enantioselective hydrolysis of 100 mM dl-menthyl acetate at 30°C and pH 7.0, using crude BSE as biocatalyst and 10% ethanol (v/v) as cosolvent, resulted in 49.0% conversion (3 h) and 98.0% ee for the l-menthol produced, which were much better than those using commercial enzymes tested. Moreover, BSE exhibited strong tolerance against high substrate concentration (up to 500 mM), and the concentration of l-menthol produced could reach as high as 182 mM, and more importantly, the optical purity of l-menthol produced was kept above 97% ee, which were not found in previous reports. These results imply that BSE is a potentially promising biocatalyst for the large-scale enzymatic preparation of l-menthol. Using this excellent biocatalyst, the enzymatic production of l-menthol will become a mild, efficient, inexpensive and easy-to-use "green chemistry" methodology.

Purification, properties, and substrate specificity of a carboxylesterase in pancreatic juice.

Abstract: An esterase activity was purified from rat pancreatic juice by DEAE cellulose chromatography, hydroxylapatite chromatography, and filtration through Sephadex G-100. After this procedure the enzyme was purified 200 times with a yield of 12%. The enzyme had a molecular weight of around 70,000 and an isoelectric point of 5.0. It had a wide substrate specificity and hydrolysed water-soluble esters as well as water-insoluble esters when dispersed with bile salt. Bile salt strongly stimulated the esterase activity, caused aggregation of the enzyme monomer into a polymer form, and protected the activity against proteolytic inactivation. On the basis of the low substrate specificity, the enzyme should be classified as a carboxylic esterase. It most probably is identical with sterolester hydrolase.

A Collagenolytic Enzyme from Aspergillus oryzae

Abstract: 1 A highly purified protease has been prepared from culture filtrates of Aspergillus oryzae. The process consists of four steps, namely the dialysis of the starting material, precipitation with acetone, separation by carrier-free electrophoresis and fractionation with acetone. The specific activity of the protease is increased 40 times or more. The product was shown to be a single substance by means of the ultracentrifuge, disc electrophoresis and immuno-electrophoresis. As far as investigated, it is free of non-specific activities. 2 The molecular weight was found to be about 20,000 by elution from a Sephadex G-75 column, by ultracentrifugation and by amino acid analysis. The pH optimum normally lies between 9 and 10. The protease cannot be activated with metal ions; it is, however, inhibited by Cu2+, Hg2+ and Zn2+ ions. It is also inhibited by di-isopropyl phosphofluoridate and other compounds that react specifically with serine. 3 The protease splits denatured proteins preferentially, but not solely, at the peptide bonds of amino acids with acid side chains as shown by investigations on long-chain model peptides. It also digests native collagen. The mode of splitting is the same as that by which the collagenase from Clostridium histolyticum splits the apolar regions. However, bonds involving hydroxyproline appear to be resistant to attack by the Aspergillus enzyme. In addition, the protease described here is capable of digesting bonds of the polar regions of the native collagen molecule. The protease also acts as an esterase. 4 On the basis of the various types of proteolytic specificity found for the protease a new concept is put forward for understanding collagen breakdown in vivo and in vitro.

Purification and properties of an esterase from the yeast Saccharomyces cerevisiae and identification of the encoding gene.

Abstract: We purified an intracellular esterase that can function as anS-formylglutathione hydrolase from the yeastSaccharomyces cerevisiae. Its molecular mass was 40 kDa, as determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was 5.0 by isoelectric focusing. The enzyme activity was optimal at 50°C and pH 7.0. The corresponding gene, YJLO68C, was identified by its N-terminal amino acid sequence and is not essential for cell viability. Null mutants have reduced esterase activities and grow slowly in the presence of formaldehyde. This enzyme may be involved in the detoxification of formaldehyde, which can be metabolized toS-formylglutathione by S. cerevisiae.