- Positional specificity of Flavobacterium johnsoniae acetylxylan esterase and acetyl group migration on xylan main chain
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A new Flavovacterium johnsoniae isolate encodes an enzyme that is essentially identical with a recently discovered novel acetylxylan esterase, capable of liberating 3-O-acetyl group from 4-O-methyl-D-glucuronic acid-substituted xylopyranosyl (Xylp) residues (Razeq et al., 2018). In addition to deesterification of the 2-O-MeGlcA-substituted Xylp residues in acetylglucuronoxylan, the enzyme acts equally well on doubly acetylated Xylp residues from which it liberates only the 3-O-acetyl groups, leaving the 2-O-acetyl groups untouched. 3-O-Monoacetylated Xylp residues are attacked with a significantly reduced affinity. The resulting 2-O-acetylated xylan was used to investigate for the first time the migration of the 2-O-acetyl group to position 3 within the polysaccharide. In contrast to easy acetyl group migration along the monomeric xylopyranosides or non-reducing-end terminal Xylp residues of xylooligosaccharides, such a migration in the polymer required much longer heating at 100 °C. The specificity of the xylan 3-O-deacetylase was, however, no so strict on acetylated methyl and 4-nitrophenyl xylopyranosides.
- Puchart, Vladimír,Gjermansen, Morten,Mastihubová, Mária,M?rkeberg Krogh, Kristian B.R.,Biely, Peter
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- Synthesis of acylated methyl β-D-xylopyranosides and their enzymic deacylations by rabbit serum esterases
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Selective pivaloylations of methyl β-D-xylopyranoside have been studied under various reaction conditions. Partially pivaloylated products were submitted to additional acetylations. The structures were established by 1H NMR spectroscopy. Representatives of acylated methyl β-D-xylopyranosides (acyl being pivaloyl, acetyl, or a combination of both) were submitted to hydrolysis catalyzed by rabbit serum and esterases isolated from rabbit serum.
- Petrovic, Vesna,Tomic, Srdanka,Ljevakovic, Durdica,Tomasic, Jelka
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