Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEXOSES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources
PubMed1978

Structure of the hexose region of Shigella sonnei phase II lipopolysaccharide with 3-deoxy-D-manno-octulosonic acid as possible immunodeterminant and its relation to Escherichia coli R1 core.

Comparative chemical analysis (methylation, gas chromatography/mass spectrometry, periodate oxidation, etc.) of the lipopolysaccharides and degraded polysaccharides derived from Shigella sonnei phase I, phase II and galactose-deficient R mutants revealed a structure as shown: (formula: see text) 3-Deoxy-D-manno-octulosonic acid (dOclA) as an immunodeterminant was observed in the passive hemolysis inhibition test by (a) selective inhibition of the phase II system by dOclA; (b) the kinetics of the change of serological activity during mild acid treatment: 1% acetic acid abolished serological activity; (c) a lack of activity in galactose-less R mutants and reactivity with Re mutants including Salmonella minnesota Re. An enhanced sensitivity of phase II lipopolysaccharide to galactose oxidase after prolonged treatment with 1% acetic acid suggests that dOclA is linked to C-6 of the terminal or subterminal galactose. dOclA as immunodeterminant could explain some different polysaccharide structures described for Escherichia coli R1 core.

Acetates↗
PubMed1979

Induction of the phosphoenolpyruvate: hexose phosphotransferase system associated with relative anaerobiosis in an obligate aerobe.

Arthrobacter pyridinolis possesses alternative transport systems for D-fructose: a respiration-coupled transport system whereby D-fructose transport occurs with concomitant oxidation of L-malate, and a phosphoenolpyruvate: D-fructose phosphotransferase system. Studies of D-fructose uptake by whole cells in the presence and absence of cyanide demonstrate that respiration-coupled transport is used almost exclusively during the first half of logarithmic growth, after which it accounts for only 15-20% of D-fructose uptake. Phosphotransferase levels are low during log phase, peak during late log, and then slowly decline. In a mutant of A. pyridinolis which requires delta-aminolevulinic acid for growth, the growth rate, cell cytochrome content, and activity of the respiration-coupled transport system increased with increasing concentrations of delta-aminolevulinic acid up to 50 microgram/ml. By contrast, phosphotransferase activity was highest in cells grown on limiting delta-aminolevulinic acid. L-Malate, which stimulates respiration-coupled transport, repressed the phosphotransferase system. The respiratory activity and the ability to release CO2 from internalized d-fructose was consistently low in D-fructose-grown cells. A cyanide-resistant cytochrome, tentatively identified as cytochrome d, appeared in the late exponential phase of growth. Isocitrate lyase activity, required for aerobic growth of this organism, declined markedly during the late exponential phase. Thus the phosphotransferase system is maximally induced, in this obligate aerobe, under conditions of relative anaerobiosis during which metabolism is primarily fermentative.

Aerobiosis↗
PubMed1985

Sugar specificity and sugar-proton interaction for the hexose-proton-symport system of Chlorella.

The substrate specificity of the glucose-proton symport system was studied to gain information about the spatial relationship between the binding sites for glucose and proton. Charged glucose analogues such as amino sugars or sugar acids were not transported by the uptake system, with the exception of 2-amino-2-deoxy-D-glucose. This glucosamine was taken up in the charged form in uniport mechanism, i.e. without symport of proton. This result was interpreted to mean that the proton-binding site of the symport system is close to the hydroxyl at carbon 2 of glucose. This interpretation was strengthened by the following facts: The steric position of hydroxyl groups at carbons 1, 2 or 3 of glucose were especially important for efficient transport. O-Methylation was not tolerated at carbon 1, but it was tolerated at carbons 3, 4 or 6. The stoichiometric flow of proton and sugar could be disturbed by removal of hydroxyl group at carbon 1 of glucose. The pH-dependence of sugar transport is sugar-specific, e.g. the amino group at carbon 2 of glucose improves transport at higher pH. The configuration at carbon 2 of glucose influences the specificity for the symported ion. It is concluded that the coupled flow of proton and glucose occurs by simultaneous coordinate movement of both in a transmembrane channel.

Biological Transport↗
PubMed1991

Glucose repression in Saccharomyces cerevisiae is directly associated with hexose phosphorylation by hexokinases PI and PII.

Genetic and biochemical analyses showed that hexokinase PII is mainly responsible for glucose repression in Saccharomyces cerevisiae, indicating a regulatory domain mediating glucose repression. Hexokinase PI/PII hybrids were constructed to identify the supposed regulatory domain and the repression behavior was observed in the respective transformants. The hybrid constructs allowed the identification of a domain (amino acid residues 102-246) associated with the fructose/glucose phosphorylation ratio. This ratio is characteristic of each isoenzyme, therefore this domain probably corresponds to the catalytic domain of hexokinases PI and PII. Glucose repression was associated with the C-terminal part of hexokinase PII, but only these constructs had high catalytic activity whereas opposite constructs were less active. Reduction of hexokinase PII activity by promoter deletion was inversely followed by a decrease in the glucose repression of invertase and maltase. These results did not support the hypothesis that a specific regulatory domain of hexokinase PII exists which is independent of the hexokinase PII catalytic domain. Gene disruptions of hexokinases further decreased repression when hexokinase PI was removed in addition to hexokinase PII. This proved that hexokinase PI also has some function in glucose repression. Stable hexokinase PI overproducers were nearly as effective for glucose repression as hexokinase PII. This showed that hexokinase PI is also capable of mediating glucose repression. All these results demonstrated that catalytically active hexokinases are indispensable for glucose repression. To rule out any further glycolytic reactions necessary for glucose repression, phosphoglucoisomerase activity was gradually reduced. Cells with residual phosphoglucoisomerase activities of less than 10% showed reduced growth on glucose. Even 1% residual activity was sufficient for normal glucose repression, which proved that additional glycolytic reactions are not necessary for glucose repression. To verify the role of hexokinases in glucose repression, the third glucose-phosphorylating enzyme, glucokinase, was stably overexpressed in a hexokinase PI/PII double-null mutant. No strong effect on glucose repression was observed, even in strains with 2.6 U/mg glucose-phosphorylating activity, which is threefold increased compared to wild-type cells. This result indicated that glucose repression is only associated with the activity of hexokinases PI and PII and not with that of glucokinase.

Enzyme Repression↗
PubMedDate not supplied

Changes in the shape of Leishmania major promastigotes in response to hexoses, proline, and hypo-osmotic stress.

Leishmania major promastigotes in late-log phase are generally long and slender, and remain so during a 1 h incubation in buffer without exogenous substrate. When glucose, 2-deoxyglucose, fructose, mannose, or proline are added, the cells become shorter and more rounded. The shape change in response to glucose is complete within 20 min and is reversible upon incubating the cells without substrate. Galactose, 3-O-methylglucose, 6-deoxyglucose, sucrose, maltose, ribose, glycerol, alanine, glutamate or aspartate do not cause the shape change. Decreasing the osmolarity of the medium causes a rounding of the cells similar to that observed in the presence of glucose, and increasing the osmolarity inhibits the shape change in response to glucose. Inhibitors of glucose transport and 2nd messenger analogs do not affect the shape change.

Animals↗
PubMedDate not supplied

Effects of culture age and hexoses on fatty acid oxidation by Leishmania major.

The effect of culture age on the rate of oxidation of short-, medium, and long-chain fatty acids by Leishmania major promastigotes was investigated. Promastigotes from 5-day stationary phase cultures oxidized several saturated fatty acids about 3-to-4-fold faster than cells from late log phase cultures, but [10-14C]oleate was oxidized 9-fold faster. The increase in rate of oxidation was partially reversed within 5 h and almost completely reversed within 30 h after resuspending cells from a 5-day stationary culture in fresh medium. Addition of acetate, leucine, or alanine caused moderate inhibitions of [1-14C]palmitate oxidation, while glycerol had little effect. Glucose, however, was a powerful inhibitor of the oxidation of [1-14C]palmitate and of [1-14C]octanoate. Mannose and fructose were also strong inhibitors of palmitate oxidation, but neither galactose, 2-deoxyglucose or 6-deoxyglucose caused appreciable inhibition. The extent of inhibition by acetate increased with increasing culture age, whereas inhibition by glucose decreased. In addition to demonstrating a reversible rise in beta-oxidation capacity with culture age, these data also demonstrate a hitherto unrecognized strong and culture age-dependent inhibition of fatty acid oxidation by glucose.

Acetates↗
PubMed2000

Aldolases of the DhnA family: a possible solution to the problem of pentose and hexose biosynthesis in archaea.

Sequence analysis of the recently identified class I aldolase of Escherichia coli (dhnA gene product) helped to identify its homologs in Chlamydia trachomatis, Chlamydiophyla pneumoniae and in each of the completely sequenced archaeal genomes. Iterative database searches revealed sequence similarities between the DhnA-family enzymes, deoxyribose phosphate aldolases and bacterial (class II) fructose bisphosphate aldolases and allowed prediction of similar three-dimensional structures (TIM-barrel fold) in all these enzymes. The Schiff base-forming lysyl residues of DhnA and deoxyribose phosphate aldolase are conserved in all members of the DhnA and deoxyribose phosphate aldolase families, indicating that these enzymes share common features with both class I and class II aldolases. The DhnA-family enzymes are predicted to possess an aldolase activity and to play a critical role in sugar biosynthesis in archaea.

Amino Acid Sequence↗