77217-82-4Relevant academic research and scientific papers
A new family of carbohydrate esterases is represented by a GDSL hydrolase/acetylxylan esterase from Geobacillus stearothermophilus
Alalouf, Onit,Balazs, Yael,Volkinshtein, Margarita,Grimpel, Yael,Shoham, Gil,Shoham, Yuval
body text, p. 41993 - 42001 (2012/03/27)
Acetylxylan esterases hydrolyze the ester linkages of acetyl groups at positions 2 and/or 3 of the xylose moieties in xylan and play an important role in enhancing the accessibility of xylanases to the xylan backbone. The hemicellulolytic system of the thermophilic bacterium Geobacillus stearothermophilus T-6 comprises a putative acetylxylan esterase gene, axe2. The gene product belongs to the GDSL hydrolase family and does not share sequence homology with any of the carbohydrate esterases in the CAZy Database. The axe2 gene is induced by xylose, and the purified gene product completely deacetylates xylobiose peracetate (fully acetylated) and hydrolyzes the synthetic substrates 2-naphthyl acetate, 4-nitrophenyl acetate, 4-methylumbelliferyl acetate, and phenyl acetate. The pH profiles for kcat and kcat/K m suggest the existence of two ionizable groups affecting the binding of the substrate to the enzyme. Using NMR spectroscopy, the regioselectivity of Axe2 was directly determined with the aid of one-dimensional selective total correlation spectroscopy. Methyl 2,3,4-tri-O-acetyl-β-D-xylopyranoside was rapidly deacetylated at position 2 or at positions 3 and 4 to give either diacetyl or monoacetyl intermediates, respectively; methyl 2,3,4,6-tetra-O- acetyl-β-D-glucopyranoside was initially deacetylated at position 6. In both cases, the complete hydrolysis of the intermediates occurred at a much slower rate, suggesting that the preferred substrate is the peracetate sugar form. Site-directed mutagenesis of Ser-15, His-194, and Asp- 191 resulted in complete inactivation of the enzyme, consistent with their role as the catalytic triad. Overall, our results show that Axe2 is a serine acetylxylan esterase representing a new carbohydrate esterase family.
An efficient chemoenzymatic route to methyl 4-O-benzyl-2,3-anhydro-β- D-lyxopyranoside from methyl β-D-xylopyranoside
Mastihubova, Maria,Mastihuba, Vladimir,Biely, Peter
, p. 425 - 428 (2007/10/03)
Methyl 4-O-benzyl-2,3-anhydro-β-D-lyxopyranoside, an intermediate for the preparation of methyl β-D-xylopyranoside derivatives modified at C-2, was obtained in five steps in 58% yield. The synthetic sequence starts from methyl β-D-xylopyranoside through two main steps involving regioselective enzymatic acetylation and deacetylation catalyzed by lipase PS.
Regioselective Acetylations of Alkyl β-D-Xylopyranosides by Use of Lipase PS in Organic Solvents and Application to the Chemoenzymatic Synthesis of Oligosaccharides
Lopez, Rosa,Montero, Esther,Sanchez, Felicitas,Canada, Javier,Fernandez-Mayoralas, Alfonso
, p. 7027 - 7032 (2007/10/02)
Aglycon structure and solvent can change the regioselectivity of the acetylation of alkyl β-D-xylopyranosides, catalyzed by lipase PS.The acetylation of methyl β-D-xylopyranoside (3) in acetonitrile gave the 3,4-diacetate 4 exclusively, whereas the reacti
METHANOLYSIS OF ACETYLATED SUGARS AND GLYCOSIDES IN THE PRESENCE OF TIN OXIDES AND ALKOXIDES
Herzig, Jacob,Nudelman, Abraham,Gottlieb, Hugo E.
, p. 21 - 28 (2007/10/02)
A simple, regioselective O-deacetylation procedure is described which involves > OH > OMe.No acyl migration took place under the reaction conditions.
