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D J Walton

Publications and source records attributed to D J Walton.

29 records · Page 2Linked to original sources
PubMed1986

Non-enzymic glycation of proteins: analysis of N-(1-deoxyhexitol-1-yl)amino acids by high-performance liquid chromatography.

A method for determining the extent of non-enzymic glycation (originally called "glycosylation") of both lysyl and N-terminal residues of a protein is described. The glycated protein is treated with sodium borohydride, and is then subjected to acid-catalysed hydrolysis. The resulting N-(1-deoxy-D-hexitol-1-yl)amino acids are separated by cation-exchange high-performance liquid chromatography (l.c.), and detected by a post-column reaction with periodate. The method has been applied successfully to samples of human hemoglobin and human serum albumin, for measurement of numbers of valine-attached and of lysine-attached N-(1-deoxy-D-fructos-1-yl) groups per protein molecule.

Amino Acids↗
PubMed1984

Synthesis of N-(1-deoxyhexitol-1-yl)amino acids, reference compounds for the nonenzymic glycosylation of proteins.

The N-(1-deoxy-D-mannitol-1-yl) and N-(1-deoxy-D-glucitol-1-yl) derivatives of L-valine, L-alanine, L-threonine, and L-leucine were prepared by reductive amination of D-mannose and D-glucose with the appropriate amino acids, in the presence of sodium cyanoborohydride. N epsilon-(1-Deoxy-D-mannitol-1-yl)- and N epsilon-(1-deoxy-D-glucitol-1-yl)-L-lysine were prepared by similar reactions of hexoses with N alpha-tert-butoxycarbonyl and N alpha-benzyloxycarbonyl-L-lysine, followed by removal of the protecting groups. The structures were confirmed by 1H-n.m.r. spectroscopy, which showed that each compound was completely free of its C-2 epimer. The synthetic compounds may be used as reference compounds for the identification of N-(1-deoxyhexitol-1-yl)amino acids formed when N-(1-deoxy-D-fructose-1-yl) groups of nonenzymically glycosylated proteins, of the hemoglobin A1c type, are reduced with sodium borohydride, and the protein is subjected to acid-catalyzed hydrolysis.

Amino Acids↗
PubMed1984

Analysis of bound carbohydrates of human lens fractions by gas-liquid chromatography.

The bound carbohydrates of noncataractous , decapsulated, human lenses have been examined. The hexoses and hexosamines of the water-soluble, water-insoluble nonmembrane, and membrane fractions of lenses from six age groups were determined by gas-liquid chromatography. The plasma membrane contains 60-70% of all bound carbohydrates, including glucose, galactose, mannose, fucose, glucosamine, and galactosamine. These also occur in the water-insoluble nonmembrane fraction, suggesting that the latter contains glycoproteins. The water-soluble fraction contains glucose, galactose, and mannose.

Adolescent↗
PubMed1979

A compound representing the D-glycerate terminus of the methylglucose-containing polysaccharide of Mycobacterium smegmatis.

In order to study the structure of the methylglucose-containing polysaccharide (MGP) of Mycobacterium smegmatis by NMR spectroscopy, we have prepared the model compound O-alpha-D-glucopyranosyl-(1 leads to 2)-D-glyceric acid. This compound, which represents the aglycon-containing terminus of MGP, was made from leucorse [O-alpha-D-glucopyranosyl-(1 leads to 5)-D-fructopyranose] by successive treatment with sodium borohydride, lead tetraacetate, and hypobromite. The structure of O-alpha-D-glucopyranosy.-(1 leads to 2)-D-glyceric acid was confirmed by chemical and enzymic methods. 13C and 1H NMR spectra of this compound, together with spectra of several disaccharides, were obtained for future reference in the polysaccharide study. The nine resonances in the 13C spectrum were assigned by comparison with the spectrum of methyl alpha-D-glucopyranoside. Analysis of the 1H NMR spectrum showed that the two methylene protons on C-3 of the glycerate moiety were less equivalent in the sodium salt than in the acid. This may be attributable to hydrogen bonding between the carboxylate and the hydrogen atom of the glycerate 3-hydroxyl group.

Carbohydrate Conformation↗
PubMed1978

A comparative study of the tissue and species distribution of NADPH-dependent aldehyde reductase.

1. NADPH-dependent aldehyde reductase (AR) is widely distributed among animal species. It also occurs in flowering plants and fungi (yeast). 2. AR is located mainly in the kidney or renal tissue of all species examined, with the exception of fish where it occurs mainly in the liver. 3. The enzyme from each species is monomeric and has a molecular weight between 30,000 and 40,000 daltons. 4. The enzymes exhibit similar substrate specificities and pH profiles and are inhibited by barbiturates. 5. In the reduction of D-glyceraldehyde the monomeric AR of each species catalyzes the stereospecific transfer of the A hydrogen from NADPH.

Alcohol Oxidoreductases↗
PubMed1975

Properties of the nicotinamide adenine dinucleotide phosphate-dependent aldehyde reductase from pig kidney. Amino acid composition, reactivity of cysteinyl residues, and stereochemistry of D-glyceraldehyde reduction.

Some physical and chemical properties of the monomeric NADP+-dependent aldehyde reductase (previously called TPN-L-hexonate dehydrogenase or D-glucuronate reductase) from pig kidney have been examined. The amino acid composition has been determined. Four of the five thiol groups react with p-mercuribenzoate at pH 7, with no resulting loss of catalytic activity. High concentrations of p-mercuribenzoate cause complete enzyme inhibition, which can be partly reversed by addition of aldehyde reductase is low (9%, estimated from the ellipticity at 208 nm), and 70 to 80% of the tyrosine and tryptophan residues aare buried within the molecule. One molecule of NADPH binds to the enzyme (Kp equal 25 muM), causing a blue shift and enhancement of the coenzyme fluorescence, and suggesting that the environment of the active site is hydrophobic. In the reduction of D-glyceraldehyde, catalyzed by aldehyde reductase, the pro-4R "A" hydrogen of NADPH attacks the re face of the carbonyl group. This stereospecificity is the same as in the reductions of D-glyceraldehyde and acetaldehyde effected by rabbit muscle dehydrogenase and liver alcohol dehydrogenase, respectively.

Aldehyde Oxidoreductases↗