The conformation of 1,6-anhydrolactose and its hexa-acetate in solution

Rivera‐Sagredo, Alfonso; Jiménez‐Barbero, Jesús

doi:10.1016/0008-6215(91)84024-9

Cited by 11 publications

(4 citation statements)

References 23 publications

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“…To address the issue of the importance of the glucose moiety, a drastic change in the disaccharide structure was considered. The overall shape of 1,6-anhydrolactose, shows some differences compared to that of methyl P-lactoside [36], although it still retains two hydroxyl groups in the D-glucopyranose moiety. When 1 ,h-anhydrolactose was assayed with lactase, no hydrolysis products could be detected.…”

Section: Resultsmentioning

confidence: 99%

Substrate specificity of small‐intestinal lactase

Rivera‐Sagredo

Cañada

Nieto

et al. 1992

European Journal of Biochemistry

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Lactase-phlorizin hydrolase is a disaccharidase present in the small intestine of mammals. This enzyme has two active sites, one being responsible for the hydrolysis of lactose. Lactase activity is thought to be selective towards glycosides with a hydrophilic aglycon. In this work, we report a systematic study on the importance of each hydroxyl group in the substrate molecule for lactase activity. For this purpose, all of the monodeoxy derivatives of methyl b-lactoside and other lactose analogues are studied as lactase substrates. With respect to the galactose moiety, it is shown here that HO-3' and HO-2' are necessary for hydrolysis of the substrates by lactase. Using these chemically modified substrates, it has been confirmed that lactase does not behave as a typical P-galactosidase, since it does not show an absolute selectivity with respect to substitution and stereochemistry at C4' in the galactose moiety of the substrate. However, the glucose moiety, in particular the HO-6, appears to be important for substrate hydrolysis, although none of the hydroxyl groups seemed to be essential. In order to differentiate both activities of the enzyme, a new assay for the phlorizin-hydrolase activity has also been developed.Small-intestinal disaccharidases in higher animals are located in the luminal membrane of intestinal mucose where they hydrolyze the disaccharides in the diet and the oligosaccharides that arise in the intestinal lumen after a-amiIolysis of starch [l, 21. Lactase is the small-intestinal disaccharidase that splits the major 8-glycoside of the diet, lactose, to give glucose and galactose (Scheme 1). The enzyme has been the subject of considerable investigation because of its involvement in the most frequent genetically based syndrome in man, known as adult-type alactasia or lactose intolerance in the adult resulting in a remarkable decrease in lactase activity in adulthood which affects more than 33% of adult humans [I, 3,4].A biological clock appears to exist, causing a marked decline of lactase after weaning, except for individuals whose ancestors are dependent on a substantial consumption of milk and milk-derived products.It has been known for some time that, in addition to lactase activity, the enzyme carries a P-glucosidase activity refered to as phlorizin hydrolase [5-81, which is in fact a glycosylceramidase [9]. The enzyme is therefore named lactasephlorizin hydrolase or the intestinal P-glycosidase complex. We have now carried out a systematic study of the substrate specificity with respect to the lactase site of the bglycosidase complex from sheep small intestine, using chemically modified methyl P-lactoside derivatives. Methyl P-lactoside rather than lactose, has been used as a reference compound in order to simplify the analysis of the reaction mixtures. These chcmically modified substrates have been frequently used in the study of enzyme mechanisms [13 -161 and have proved extremely useful in probing the combining sites for the elucidation of specific interactions between proteins and carb...

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Section: Resultsmentioning

confidence: 99%

Substrate specificity of small‐intestinal lactase

Rivera‐Sagredo

Cañada

Nieto

et al. 1992

European Journal of Biochemistry

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“…The conformations of 1,6-anhydro-β--glucopyranoses are known to be solvent-dependent, and appreciable populations of boat-like conformers have been observed in DMSO. [42,43] Analogously, the hexadecanoyl and naphthaloyl amido-substituted analogue of 6 (compound 3) has also been shown to present a chair conformation in [D]chloroform over the 297Ϫ318-K temperature range.…”

Section: Amides 4؊6 In Water Solution and Their Analogues 1؊3 In Chlomentioning

confidence: 99%

Investigation of the Hydrogen Bonding Properties of a Series of Monosaccharides in Aqueous Media by 1H NMR and IR Spectroscopy

et al. 2002

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A technique, based on 1 H NMR and IR experiments, to characterise intramolecular hydrogen bonds in aqueous medium in a series of amino, amido and ammonium sugar derivatives has been established. Three groups of molecules, representing amides (4, 5 and 6), amines (7 and 8) and ammonium salts (chlorides 9 and 10, and phosphates 11 and 12), with different relative configurations of their functional groups, have been investigated to assess the effect of the nature and the stereochemistry of these groups on the hydrogen-bonding features of the sugar. The deduced features in water solution are compared to those obtained previously in nonpolar solvents. The phosphate salts of amines 7 and 8 (11 and 12)

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“…Fully solvated OH groups show large j Dd/DT j values, while OH groups Helvetica Chimica Acta ± Vol. 83 (2000) 1010 11 ) Sometimes only smaller J(2,3) and J(3,4) values ( 2 Hz) have been assigned to the 1 C 4 conformer (see, e.g., [46]), whereas J(2,3) and J(3,4) values of 3 ± 4 Hz should indicate an equilibrium between the 1 C 4 and the B 3,O conformer which shows typical J(2,3) and J(3,4) values of 8 ± 10.5 Hz [45]. However, these small changes of J(2,3) and J(3,4) can be easily explained by a slight flattening of the 1 C 4 chair influenced by the substituents and the solvent.…”

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1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Bernet

Vasella

2000

HCA

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The interpretation of 1H‐NMR chemical shifts, coupling constants, and coefficients of temperature dependence (δ(OH), J(H,OH), and Δδ(OH)/ΔT values) evidences that, in (D6)DMSO solution, the signal of an OH group involved as donor in an intramolecular H‐bond to a hydroxy or alkoxy group is shifted upfield, whereas the signal of an OH group acting as acceptor of an intramolecular H‐bond and as donor in an intermolecular H‐bond to (D6)DMSO is shifted downfield. The relative strength of the intramolecular H‐bond depends on co‐operativity and on the acidity of OH groups. The acidity of OH groups is enhanced when they are in an antiparallel orientation to a C−O bond. A comparison of the 1H‐NMR spectra of alcohols in CDCl3 and (D6)DMSO allows discrimination between weak and strong intramolecular H‐bonds. Consideration of IR spectra (CHCl3 or CH2Cl2) shows that the rule according to which the downfield shift of δ(OH) for H‐bonded alcohols in CDCl3 parallels the strength of the H‐bond is valid only for alcohols forming strong intramolecular H‐bonds. The combined analysis of J(H,OH) and δ(OH) values is illustrated by the interpretation of the spectra of the epoxyalcohols 14 and 15 (Fig. 3). H‐Bonding of hexopyranoses, hexulopyranoses, alkyl hexopyranosides, alkyl 4,6‐O‐benzylidenehexopyranosides, levoglucosans, and inositols in (D6)DMSO was investigated. Fully solvated non‐anomeric equatorial OH groups lacking a vicinal axial OR group (R=H or alkyl, or (alkoxy)alkyl) show characteristic J(H,OH) values of 4.5 – 5.5 Hz and fully solvated non‐anomeric axial OH groups lacking an axial OR group in β‐position are characterized by J(H,OH) values of 4.2 – 4.4 Hz (Figs. 4 – 6). Non‐anomeric equatorial OH groups vicinal to an axial OR group are involved in a partial intramolecular H‐bond (J(H,OH)=5.4 – 7.4 Hz), whereas non‐anomeric equatorial OH groups vicinal to two axial OR form partial bifurcated H‐bonds (J(H,OH)=5.8 – 9.5 Hz). Non‐anomeric axial OH groups form partial intramolecular H‐bonds to a cis‐1.3‐diaxial alkoxy group (as in 29 and 41: J(H,OH)=4.8 – 5.0 Hz). The persistence of such a H‐bond is enhanced when there is an additional H‐bond acceptor, such as the ring O‐atom (43 – 47: J(H,OH)=5.6 – 7.6 Hz; 32 and 33: 10.5 – 11.3 Hz). The (partial) intramolecular H‐bonds lead to an upfield shift (relative to the signal of a fully solvated OH in a similar surrounding) for the signal of the H‐donor. The shift may also be related to the signal of the fully solvated, equatorial HO−C(2), HO−C(3), and HO−C(4) of β‐D‐glucopyranose (16: 4.81 ppm) by using the following increments: −0.3 ppm for an axial OH group, 0.2 – 0.25 ppm for replacing a vicinal OH by an OR group, ca. 0.1 ppm for replacing another OH by an OR group, 0.2 ppm for an antiperiplanar C−O bond, −0.3 ppm if a vicinal OH group is (partially) H‐bonded to another OR group, and −0.4 to −0.6 for both OH groups of a vicinal diol moiety involved in (partial) divergent H‐bonds. Flip‐flop H‐bonds are observed between the diaxial HO−C(2) and HO−C(4) of the inositol 40 (J(H...

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The conformation of 1,6-anhydrolactose and its hexa-acetate in solution

Cited by 11 publications

References 23 publications

Substrate specificity of small‐intestinal lactase

Substrate specificity of small‐intestinal lactase

Investigation of the Hydrogen Bonding Properties of a Series of Monosaccharides in Aqueous Media by 1H NMR and IR Spectroscopy

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

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