Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sorbose”

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 37 records · Page 2Linked to original sources
PubMed1997

Evidence from studies of temperature-dependent changes of D-glucose, D-mannose and L-sorbose permeability that different states of activation of the human erythrocyte hexose transporter exist for good and bad substrates.

(1) The inhibition constant of L-sorbose flux from fresh human erythrocytes by D-glucose, Ki(sorbose) increases on cooling from 50 degrees C to 30 degrees C from 5.15 +/- 0.89 mM to 12.24 +/- 1.9 mM; the Ki(sorbose) of D-mannose increases similarly, indicating that the process is endothermic. (2) The activation energy Ea(sorbose) of net L-sorbose exit is 62.9 +/- 3.1 kJ/mol; in the co-presence of 5 mM D-glucose Ea(sorbose) is reduced to 41.7 +/- 1.6 kJ/mol (P < 0.005). (3) Cooling from 35 degrees C to 21 degrees C decreases the Ki(inf, cis) of auto-inhibition of D-glucose net exit from 5.2 +/- 0.3 mM to 1.36 +/- 0.06 mM; the Ki(inf, cis) of D-mannose falls from 10.9 +/- 1.65 mM to 5.7 +/- 0.3 mM. (4) The activation energy of D-glucose zero-trans net exit is 34.7 +/- 2.1 kJ/mol and that of D-mannose exit is 69.4 +/- 3.7 kJ/mol (P < 0.0025). (5) The exothermic and exergonic processes of auto-inhibition of D-glucose net exit are larger than those for D-mannose (P < 0.03). These data are consistent with D-glucose binding promoting an activated transporter state which following dissociation transiently remains; if an L-sorbose molecule binds within the relaxation time after D-glucose dissociation, it will have a higher mobility than otherwise. Cooling slows the relaxation time of the activated state hence raises the probability that L-sorbose will bind to the glucose-activated transporter. D-Glucose donates twice as much energy to the transporter as D-mannose, consequently produces more facilitation of flux. This view is inconsistent with the alternating carrier model of sugar transport in which net flux is considered to be rate-limited by return of the empty carrier, but is consistent with fixed two-site models.

Cell Membrane Permeability↗
PubMed2000

Genetics of L-sorbose transport and metabolism in Lactobacillus casei.

Genes encoding L-sorbose metabolism of Lactobacillus casei ATCC 393 have been identified on a 6.8-kb chromosomal DNA fragment. Sequence analysis revealed seven complete genes and a partial open reading frame transcribed as two units. The deduced amino acid sequences of the first transcriptional unit (sorRE) showed high similarity to the transcriptional regulator and the L-sorbose-1-phosphate reductase of the sorbose (sor) operon from Klebsiella pneumoniae. The other genes are transcribed as one unit (sorFABCDG) in opposite direction to sorRE. The deduced peptide sequence of sorF showed homology with the D-sorbitol-6-phosphate dehydrogenase encoded in the sor operon from K. pneumoniae and sorABCD to components of the mannose phosphotransferase system (PTS) family but especially to domains EIIA, EIIB, EIIC and EIID of the phosphoenolpyruvate-dependent L-sorbose PTS from K. pneumoniae. Finally, the deduced amino acid sequence of a truncated gene (sorG) located downstream of sorD presented high similarity with ketose-1,6-bisphosphate aldolases. Results of studies on enzyme activities and transcriptional analysis revealed that the two gene clusters, sorRE and sorFABCDG, are induced by L-sorbose and subject to catabolite repression by D-glucose. Data indicating that the catabolite repression is mediated by components of the PTS elements and by CcpA, are presented. Results of sugar uptake assays in L. casei wild-type and sorBC mutant strains indicated that L-sorbose is taken up by L-sorbose-specific enzyme II and that L. casei contains an inducible D-fructose-specific PTS. Results of growth analysis of those strains and a man sorBC double mutant suggested that L-sorbose is probably also transported by the D-mannose PTS. We also present evidence, from studies on a sorR mutant, suggesting that the sorR gene encodes a positive regulator of the two sor operons. Sequence alignment of SorR, SorC (K. pneumoniae), and DeoR (Bacillus subtilis) revealed that they might constitute a new group of transcriptional regulators.

Amino Acid Sequence↗
PubMed1977

[Researches to the conversion of sorbit into sorbose by Acetobacter suboxydans (author's transl)].

The production of sorbose by Acetobacter suboxydans (4) is closely related to the concentration of sorbit in the medium. An increasing concentration of sorbit gives rise to the inhibition of cell reproduction; followed by a decrease of sorbose content in the culture medium. The decrease of sorbose yield in concentrations of about 15% sorbit in medium indicates the decreasing metabolism rate of the total population of Acetobacter suboxydans (4) culture and does not refer to the ability of the individual bacterium cell to produce sorbose. Relevant research work showed, that sorbose production for each bacterium cell distinctly increased with the decrease of the number of cells in a population of Acetobacter suboxydans (4) as a consequence of the application of an increased sorbit concentration. An unrestrained reproduction of bacteria could be obtained by exluding all factors involved in the contamination of sorbit and exhibiting toxic effects. Therefore the organisms could be offered a greater concentration of sorbit for conversion into sorbose. Thus sorbose yield would be increased, respectively. The total conversion of the C-source into sorbose could not be obtained with Acetobacter ruboxydans (4).

Acetobacter↗
PubMed1999

L-Sorbose but not D-tagatose induces hemolysis of dog erythrocytes in vitro.

Previous investigations have demonstrated that L-sorbose induces hemolysis of dog erythrocytes. This effect is probably the consequence of an ATP depletion of the red blood cells subsequent to inhibition of hexokinase, and thus the glycolytic pathway, by sorbose 1-phosphate. In the present study, the susceptibility of dog erythrocytes to D-tagatose, a stereoisomer of L-sorbose, was examined. Washed dog erythrocytes were suspended in Hanks' balanced salt solution (HBSS, containing 5.6 mM glucose) with or without the addition of 0.6, 6, and 60 mM L-sorbose or D-tagatose, or in HBSS with total glucose concentrations of 5.6, 6 and 60 mM D-glucose. After incubation for 24 h at 34 degrees C, the suspensions were centrifuged, and the percentage of hemolysis was determined by measuring the hemoglobin in the sediment and the supernatant. The amount of hemoglobin released in the medium did not differ significantly between the control (HBSS) and the test incubations with glucose or D-tagatose supplementation. In contrast, the addition of 6 and 60 mM L-sorbose resulted in significant hemolysis. At the low dose (0.6 mM), L-sorbose did not have an adverse effect. It is concluded that D-tagatose, unlike L-sorbose, does not have a hemolytic effect on canine erythrocytes.

Animals↗
PubMed1991

Feeding behavior in growing rats fed diets containing sorbose.

The effect of dietary sorbose on food and water consumption was investigated in growing rats. Rats (26-day old) were fed diets containing 0, 100, 200 or 300 g sorbose/kg diet for 5 weeks in Experiment 1. Daily food and water intakes were measured at day 0, 7, 14, 21, 28 and 35. Absolute food intake (g) until day 21 decreased linearly with increasing sorbose levels and so did relative food intake (g/100 g b.wt.) until day 7. In contrast, relative water intake (ml/100 g b.wt.) and water:food intake ratio (ml/g) remained high by day 7 with increasing sorbose levels. In Experiment 2, the effect of sorbose on the short-term food intake was compared with those of glucose, sucrose and maltitol in growing rats (25-day old) at a level of 100 g/kg diet in order to investigate how quickly reduced food intake would be induced by sorbose consumption. Cumulative food intake was determined every hour for the first ten hours, then at two-hour intervals thereafter during the 24-hour period that followed feeding. As rapid as 6 hours after feeding, cumulative food intake significantly decreased in sorbose-fed animals compared with other dietary groups. It was concluded that sorbose consumption decreased the food intake of growing rats from 6 hours to a few weeks after feeding, but this inhibitory effect disappeared afterwards.

Animals↗
PubMed1972

Effect of L-sorbose on polysaccharide synthetases of Neurospora crassa (glycogen- -1,3-glucan-morphology-cell wall-digitonin-particulate enzymes).

Neurospora glycogen synthetase (EC 2.4.1.11) occurs in 100,000 x g particles. The two forms (glucose-6-phosphate dependent-independent) of glycogen synthetase were solubilized and separated by digitonin treatment of the 100,000 x g particles. Glucan synthetase activity of Neurospora was found only in a cell-wall preparation. These two enzymes have been characterized in relation to the paramorphogenic action of sorbose. Sorbose-grown cultures showed a marked decrease in the specific activity of both enzymes, as compared to sucrose-grown wild-type cultures. Sorbose inhibited the activity of the wild-type enzymes both in vivo and in vitro. In the presence of 5 mM sorbose incorporation of [(14)C]glucose from [(14)C]uridinediphosphate glucose into glycogen by the dependent form of glycogen synthetase was completely inhibited. Thus, the paramorphogenic action of sorbose seems to result from its inhibition of these enzymes of cell-wall biosynthesis. Activities of the enzymes from the sorbose-resistant mutant, patch, were not affected by sorbose either in vivo or in vitro.

Carbon Isotopes↗
PubMed1982

Genes for l-sorbose utilization in Escherichia coli.

Amongst forty wild strains of Escherichia coli, nine used L-sorbose as a source of carbon and energy and two mutated to use it. Laboratory strains K12, B and C were L-sorbose-negative. Genes for L-sorbose utilization (sor+) were transferred to K12 from six wild strains; genes conferring the mutable phenotype were also transferred. All were cotransducible with metA at 90 min on the linkage map. The most probable gene order was met ace sor pgi mal. Complementation tests identified two genes for L-sorbose utilization. Genetical evidence showed that the catabolite repressor protein of K12 exerted positive control over sor+ genes introduced into K12. The genes for phosphofructokinase (pfkA), the phosphocarrier protein (ptsH) and phosphotransferase enzyme I (ptsI) were required for utilization of L-sorbose. The frequency of transduction of sor+ was low when selection was made for sor+, because L-sorbose partially inhibited the growth of both L-sorbose-negative strains and K12 (sor+) strains. Uridine, thymidine and sorbitol each annulled the inhibition of growth and increased the frequency of transduction of sor+.

Escherichia coli↗
PubMed1990

Regulation of lipid metabolism by dietary sorbose in laying hens.

Single Comb White Leghorn laying hens received ad libitum diets (10 birds per diet) containing varying concentrations of sorbose (0, 100, and 200 g/kg diet) for 4 wk. Body weight gain and feed intake decreased with increasing dietary sorbose. Serum triglyceride, cholesterol, low density lipoprotein, very low density lipoprotein, and chylomicron levels were significantly reduced, in dose-dependent fashions, as dietary sorbose increased, whereas serum glucose level remained unchanged by the dietary regimens. Absolute and relative weights of abdominal fat were also decreased by increasing dietary sorbose. Liver color improved; it became less white and less yellow with the supplement of dietary sorbose. Hen-day egg production rate was not affected with dietary sorbose, and hence, it has been shown that dietary sorbose can be used as a potential regulator of lipid metabolism in the laying hen.

Adipose Tissue↗
PubMed1994

Mechanism of hemolysis of canine erythrocytes induced by L-sorbose.

The cause of species difference in the susceptibility of erythrocytes to L-sorbose, and the difference in the hemolytic effect of sorbose on high potassium-containing (HK) and low potassium-containing (LK) canine erythrocytes were examined. L-Sorbose was phosphorylated in canine erythrocytes, but not in human erythrocytes. Furthermore, sorbose-1-phosphate, a metabolite of L-sorbose, strongly inhibited the hexokinase of LK canine erythrocytes, but not that of HK canine erythrocytes. These results strongly indicated that inhibition of hexokinase by sorbose-1-phosphate in LK erythrocytes induced severe glycolytic limitation in these cells, resulting in hemolysis, and that HK erythrocytes are resistant to sorbose-induced hemolysis because these cells have a high hexokinase activity.

Animals↗
PubMed1977

[Effects of dimethylsulfoxide and salicine on the delayed adaption on sorbose and dulcitol of Salmonellae (author's transl)].

Among the majority of Salmonella strains splitting sorbose or dulcitol with delay dimethylsulfoxide shortens the latent period preceding acid formation and abolishes the deceleration of sorbose adaption caused by salicine. In other strains, especially S. paratyphi B cultures, DMSO doesn't touch sorbose adaption directly but amplifies the restraing effect of salicine. From the whole of our findings it can be concluded that in the first group of strains sorbose adaption starts with segregation of adaptive sorbose permease positive mutants, followed by the - salicin-sensitive - induction of this permease, the appearance of mutants aditionally metabolizing sorbose constitutively, and, finally, the substrate-promoted particular growth of adapted cells. The latter category of strains, however, apparently possesses a wild type (constitutive or adaptive?) sorbose permease but splits off mutants with adaptive metabolizing enzymes the induction of which is salicine-sensitive. The amplification of the salicine effect by DMSO found in these strains might be refered to an enhancement of salicine uptake caused by DMSO.

Adaptation, Physiological↗
PubMed1991

Energy utilisation in germ-free and conventional chicks fed diets containing sorbose.

1. In experiment 1, growing conventional (CV) chicks were fed on diets containing graded amounts (0, 100, 200 and 300 g/kg diet) of sorbose from 4 to 14 d. Protein, fat and energy deposition were determined after carcase analysis. The values for growth, food efficiency, metabolisable energy (ME) and fat and energy depositions declined as the dietary sorbose content increased. 2. In experiment 2, the performances of germ-free (GF) and CV chicks fed on diets with (100 g sorbose/kg diet) or without sorbose were investigated. On both diets, body weight gain, food consumption and protein accumulation in GF chicks were significantly higher than those in CV birds. No significant differences were observed between the dietary treatment except for ME values, which were significantly lower for the sorbose diet. 3. It is suggested that dietary sorbose decreased energy utilisation, and that the microbial contribution to the utilisation of dietary sorbose was negligible in the chicken.

Animals↗
PubMed1991

Prevention of the incidence of diabetes by dietary sorbose in nonobese diabetic mice.

The effect of dietary sorbose on the prevention of the incidence of diabetes in the nonobese diabetic mouse was investigated in animals from 5 to 11 wk of age. When sucrose (200 g/kg diet) in the control diet was replaced by sorbose, body weight was significantly reduced. The blood glucose level also was lowered in mice fed sorbose, but the serum insulin level was unchanged. Glucose was not detected in the urine of mice fed the sorbose diet during the experiment, but some mice in the control group excreted glucose in urine. Relative weights of the heart, liver and left kidney were significantly higher in mice fed the sorbose diet vs. those fed the control diet. The results suggest that dietary sorbose would benefit patients with diabetes by lowering blood glucose and inhibiting urinary glucose excretion.

Administration, Oral↗
PubMed1985

The influence of L-sorbose on red cell flow properties, shape and packing ability.

Since the sweet ketohexose L-sorbose causes overt hemolysis in dogs but not in man, we examined the possibility that L-sorbose induces a "prehemolytic state" of human red cells, manifesting itself as impairment of rheological red cell properties. After 2 hours incubation at 37 degrees C relative viscosity of red cell suspensions measured by radial spreading in filter paper and packing ability of red cells were normal. Incubation for 24 and 48 hours of red cells in media containing L-sorbose, glucose or no sugar showed that relative viscosity was best maintained in glucose. Relative viscosity and packing ability of red cells in L-sorbose containing suspensions decreased less than in suspensions without sugar. This difference was independent of the glucose metabolism, red cell ATP, osmolality and pH of the suspending media, but appeared to be related to different degrees of spheroechinocytic red cell shape transformation observed in different suspending media. It is possible that L-sorbose has some antiechinocytic properties and/or that it induces an alteration of red cell membrane flexibility. There is no indication of an L-sorbose induced "prehemolytic state" in human red cells.

Adenosine Triphosphate↗
PubMed1976

L-Sorbose metabolism in Agrobacterium tumefaciens.

The pathway of L-sorbose metabolism in Agrobacterium tumefaciens strain B6 was determined to be: L-sorbose leads to D-glucitol (sorbitol) leads to D-fructose leads to D-fructose-6-phosphate leads to D-glucose-6-phosphate. The reduction of L-sorbose and the oxidation of D-glucitol were mediated by NADPH- and NAD+-linked oxidoreductases, respectively. The intermediates, D-glucitol and D-fructose, were isolated from in vitro reaction mixtures by column chromatography on Dowex 1-borate, and identified enzymatically. D-Fructose was identified chemically by its 1H-NMR spectrum and the IR spectrum and the melting point of the fructosazone. D-Glucitol was characterized chemically by the melting point and the IR spectrum of its hexaacetate. A. tumefaciens ICPB TT111, a representative of another genetic race of Agrobacterium, lacked L-sorbose reductase and therefore failed to grow on L-sorbose; it grew normally on D-glucitol.

Alcohol Oxidoreductases↗
PubMed2003

The alternative D-galactose degrading pathway of Aspergillus nidulans proceeds via L-sorbose.

The catabolism of d-galactose in yeast depends on the enzymes of the Leloir pathway. In contrast, Aspergillus nidulans mutants in galactokinase ( galE) can still grow on d-galactose in the presence of ammonium-but not nitrate-ions as nitrogen source. A. nidulans galE mutants transiently accumulate high (400 mM) intracellular concentrations of galactitol, indicating that the alternative d-galactose degrading pathway may proceed via this intermediate. The enzyme degrading galactitol was identified as l-arabitol dehydrogenase, because an A. nidulans loss-of-function mutant in this enzyme ( araA1) did not show NAD(+)-dependent galactitol dehydrogenase activity, still accumulated galactitol but was unable to catabolize it thereafter, and a double galE/araA1 mutant was unable to grow on d-galactose or galactitol. The product of galactitol oxidation was identified as l-sorbose, which is a substrate for hexokinase, as evidenced by a loss of l-sorbose phosphorylating activity in an A. nidulans hexokinase ( frA1) mutant. l-Sorbose catabolism involves a hexokinase step, indicated by the inability of the frA1 mutant to grow on galactitol or l-sorbose, and by the fact that a galE/frA1 double mutant of A. nidulans was unable to grow on d-galactose. The results therefore provide evidence for an alternative pathway of d-galactose catabolism in A. nidulans that involves reduction of the d-galactose to galactitol and NAD(+)-dependent oxidation of galactitol by l-arabitol dehydrogenase to l-sorbose.

Aspergillus nidulans↗
PubMed1981

L-Sorbose phosphorylation in Escherichia coli K-12.

L-Sorbose is phosphorylated by Escherichia coli by two distinct Enzymes II of the phosphoenolpyruvate-dependent phosphotransferase system. The glucose Enzyme II (specified by the gene ptsG) phosphorylates L-sorbose with an apparent Km of 0.08 +/- 0.03 mM and V of 31.8 +/- 3.5 nmol . mg-1 . min-1 whilst the fructose Enzyme II (specified by the gene ptsF) phosphorylates it with an apparent Km of 28.9 +/- 2.7 mM and V of 20.2 +/- 0.8 nmol . mg-1 . min-1. L-Sorbose induces neither of these Enzymes II, but sorbose inhibits the growth of strains expressing either of these functions constitutively. Mutants that have lost their sensitivity to L-sorbose are found to have lost either the glucose or the fructose phosphotransferase Enzyme II.U

Escherichia coli↗
PubMed1982

The influence of uncouplers on facilitated diffusion of sorbose in Saccharomyces cerevisiae.

Sorbose uptake in Saccharomyces cerevisiae, strain Delft 1, proceeds via mediated passive transport. In the cell sorbose is distributed in at least two compartments. Efflux studies showed that sorbose uptake in one of these compartments is not readily reversible. Uncouplers of oxidative phosphorylation inhibit both transport velocity and steady-state uptake level. It could be shown that these two effects are caused by different modes of action of the uncouplers. None of these two effects could be ascribed to changes of the electrochemical H+ gradient or of the intracellular pH. It is suggested that the inhibition of uptake velocity is caused by binding of the uncoupler to the sorbose translocator, thus lowering the transport activity. The uncoupler binding site is probably located at the intracellular fragment of the carrier. The second effect, reduction of the steady-state uptake level, is probably due to blocking of sorbose influx into the compartment that exhibits poor reversibility.

2,4-Dinitrophenol↗
PubMed1992

Influence of dietary sorbose on lipogenesis in gold thioglucose-injected obese mice.

1. The influence of dietary sorbose on food intake and fatty acid synthesis of the liver and epididymal white adipose tissue (EWAT) was investigated in gold thioglucose (GTG)-injected obese mice from 12 to 14 weeks of age. 2. Sorbose was supplemented to a semi-purified diet at a level of 200 g/kg diet at the expense of sucrose. 3. On the last day of the experiment, fatty acids synthesis in the liver and EWAT was measured using an i.p. injection [1-14C]sodium acetate. 4. The decreases in body weight and food intake by dietary sorbose in GTG-injected obese mice were greater than those in control mice. 5. Lipid content and fatty acid synthesis in the liver and EWAT of control mice were not influenced by dietary sorbose. 6. In GTG-injected obese mice, the reduction of food intake by dietary sorbose suppressed fatty acid synthesis and lipid deposition in both liver and EWAT.

Animals↗