Pyranose

About: Pyranose is a research topic. Over the lifetime, 1619 publications have been published within this topic receiving 35348 citations. The topic is also known as: pyranoses & hexopyranose.

Structure of the Fusarium oxysporum endoglucanase I with a nonhydrolyzable substrate analogue: substrate distortion gives rise to the preferred axial orientation for the leaving group.

Abstract: Endoglucanase I (EG I) is a cellulase, from glycosyl hydrolase family 7, which cleaves the β-1,4 linkages of cellulose with overall retention of configuration. The structure of the EG I from Fusarium oxysporum, complexed to a nonhydrolyzable thiooligosaccharide substrate analogue, has been determined by X-ray crystallography at a resolution of 2.7 A utilizing the 4-fold noncrystallographic symmetry present in the asymmetric unit. The electron density map clearly reveals the presence of three glucosyl units of the inhibitor, consistent with the known number of sugar-binding subsites, located at the active site of the enzyme in the −2, −1, and +1 subsites, i.e., actually spanning the point of enzymatic cleavage. The pyranose ring at the point of potential enzymatic cleavage is clearly distorted from the standard 4C1 chair as was originally suggested for β-retaining enzymes by Phillips [Ford, L. O., Johnson, L. N., Machin, P. A., Phillips, D. C., & Tijan, T. (1974) J. Mol. Biol. 88, 349−371]. The distortion ...

Structural requirements for binding to the sugar-transport system of the human erythrocyte

Abstract: The structural requirements for binding to the glucose/sorbose-transport system in the human erythrocyte were explored by measuring the inhibition constants, K(i), for specifically substituted analogues of d-glucose when l-sorbose was the penetrating sugar. Derivatives in which a hydroxyl group in the d-gluco configuration was inverted, or replaced by a hydrogen atom, at C-1, C-2, C-3, C-4 or C-6 of the d-glucose molecule, all bound to the carrier, confirming that no single hydroxyl group is essential for binding to the carrier. The binding and transport of 1-deoxy-d-glucose confirmed that the sugars bind in the pyranose form. The relative inhibition constants of d-glucose and its deoxy, epimeric and fluorinated analogues are consistent with the combination of beta-d-glucopyranose with the carrier by hydrogen bonds at C-1, C-3, probably C-4, and possibly C-6 of the sugar. Both polar and non-polar substituents at C-6 enhance the affinity of d-glucose derivatives relative to d-xylose, and d-galactose derivatives relative to l-arabinose, and it is suggested that the carrier region around C-6 of the sugar may contain both hydrophobic and polar binding groups. The spatial requirements at C-1, C-2, C-3, C-4 and C-6 were explored by comparing the relative binding of d-glucose and its halogeno and O-alkyl substituents. The carrier protein closely approaches the sugar except at C-3 in the d-gluco configuration, C-4 and C-6. d-Glucal was a good inhibitor, showing that a strict chair form is not essential for binding. 3-O-(2',3'-Epoxypropyl)-d-glucose, a potential substrate-directed alkylating agent, bound to the carrier, but did not inactivate it.

Equilibria between pyranoses and furanoses. II. Aldoses

Abstract: The proton magnetic resonance spectra of the aldopentoses and aldohexoses were determined in deuterium oxide solution. The signals of the anomerio protons of the two furanose and the two pyranose forms were located; the identification of these signals is discussed. The proportions of the four forms in equilibrium solution were determined.