Fructose Utilization Research Articles

Factors Affecting Fructose Utilization and Lactic Acid Formation by Human Semen. The Role of Glucose and Pyruvic Acid

Factors Affecting Fructose Utilization and Lactic Acid Formation by Human Semen. The Role of Glucose and Pyruvic Acid

Role of fructose-1,6-diphosphatase in fructose utilization by Escherichia coli

Role of fructose-1,6-diphosphatase in fructose utilization by Escherichia coli

Pathway of fructose utilization by Escherichia coli

Esc+erichia coli grows readily on fructose as sole source of carbon. It was long assumed that the manner in which this sugar is utilized is analogous to that by which glucose enters the main metabolic pathways of the cells; this would imply the occurrence of an initial enzymatic phosphorylation by ATP of fructose to fructose-6-phosphate and ADP, followed by a second phosphorylation to fructose-l ,ddiphosphate. Enzymes catalysing both these reactions have been demonstrated to be present E. coli [ 1,2] . However, recent studies in several laboratories have cast doubt on this view, and have suggested that fructose is initially phosphorylated to fructose-l-phosphate (reaction 1) with concomitant conversion of phosphoenolpyruvate (PEP) to pyruvate. Fructose-l-phosphate is then further phosphorylated to fructose1,6-diphosphate, through the agency of an ATP-linked fructose-l-phosphate kinase (reaction 2) distinct from the action of the phosphosfructokinase that catalyses the phosphorylation of fructose-6-phosphate to fructose-l ,6-diphosphate.

Factors influencing the response of ram spermatozoa to bicarbonate and carbon dioxide.

The metabolism of washed ram spermatozoa was studied in the presence of bicarbonate or carbon dioxide or both under various conditions of incubation. The presence of respired carbon dioxide had little or no effect on the utilization of glucose or fructose by ram spermatozoa whether potassium was present or not. On the other hand, the addition of 6 mM sodium bicarbonate to a potassium-containing diluent stimulated oxygen uptake, glycolysis, and fructolysis by the spermatozoa. The effect of bicarbonate on substrate utilization did not depend on the maintenance of a constant concentration of carbon dioxide in the gas phase and was not influenced by prior exposure to bicarbonate. Substrate utilization was not stimulated by bicarbonate in the absence of potassium; there was a depression of oxygen uptake under these conditions.

The Motility and Aerobic Metabolism of Spermatozoa in Laboratory Animals with Special Reference to the Effects of Cold Shock and the Importance of Calcium for the Motility of Hamster Spermatozoa1

The metabolism and motility of epididymal spermatozoa of the hamster, rat, guinea pig, and rabbit have been studied in the presence or absence of male accessory secretions. The metabolic activity of hamster spematozoa was about three times higher than that of rat spermatozoa. In both Ringer’s solution and in 0.85% NaCl solution the motility of hamster epididymal spermatozoa was greatly decreased for about 4 hr and recovered again in the course of incubation at 37 C. This reaction seemed to be specific to hamster spermatozoa and was never observed in rat, guinea pig, and rabbit spermatozoa. The motility and respiration of hamster spermatozoa were depressed by the presence of fresh seminal vesicular fluid. However, the presence of fluids from fresh dorsal prostate or from the seminal vesicle stored at 5 C for 2 days stimulated both respiration and motility. In contrast, the presence of fluid from the ventral prostate depressed both oxygen uptake and motility of spermatozoa. A factor which can sensitize the epididymal spermatozoa to cold shock seemed to be present in the male accessory glands although the location of this factor may differ in different species. Hamster epididymal spermatozoa stopped forward motility immediately after being mixed with calcium-free solutions, although short-wave flagellation continued for a long while. In contrast, progressive motility of long duration was observed in the epididymal spermatozoa of the rat, mouse and rabbit either with or without calcium chloride in the media. The effect of calcium on the motility of hamster spermatozoa is specific to the spermatozoa themselves and is not influenced by accessory secretions. The minimal concentration of calcium chloride for the maintenance of normal motility of hamster spermatozoa was found to be 0.001 M in the medium. The motility of hamster spermatozoa was maintained by the addition of glucose, fructose, fructose-1,6-phosphate, sodium acetate, or even ATP only when calcium chloride and sodium bicarbonate were present in the medium. Calcium chloride had no effect on the oxygen uptake and fructose utilization by hamster spermatozoa, but only the presence of calcium chloride would maintain progressive motility for 12 hr. It appears that there is an intrinsic difference in the mechanism of motility of spermatozoa of the hamster and those of other species although there is little evidence to show a difference in their metabolic patterns.

Glucose utilization in muscle during uremia; in vitro study

1. 1. Rat hemidiaphragms incubated in uremic sera utilize less glucose than those incubated in control sera. Uremic sera do not inhibit the utilization of fructose. 2. 2. The concentrations of free glucose, glucose 6-phosphate and fructose 6-phosphate in diaphragms incudated in uremic sera rise, the concentration of fructose 1,6-diphosphate falls, indicating the crossover point at the level of phosphofructokinase. 3. 3. Uremic sera decrease the concentrations of pyruvate, citrate and α-ketoglutarate in diaphragms, but do not influence the concentrations of adenosine tri-, di-, or monophosphate. It is concluded that uremic sera inhibit primarily the activity of phosphofructokinase in diaphragms. The significance of citrate or adenosine phosphates in evoking this inhibition was excluded.

Conservation of wilted and unwilted grass ensiled in air‐tight metal containers with and without the addition of molasses

AbstractItalian ryegrass was ensiled in gas‐tight silos in unwilted (21% dry matter) and wilted (42% dry matter) conditions without an additive and with the addition of molasses at a mean level of 8% in the dry matter. The total dry matter losses were 8·7, 7·2, 4·5 and 5·0% for unwilted, molassed unwilted, wilted, and molassed wilted grass silages respectively. The silages were all well preserved but the extent of fermentation had been reduced in the wilted silages. The losses of individual sugars during the silage process and the products of fermentation were used to assess the pathways of fermentation. The dominant pathway of fructose utilisation was by heterolactic fermentation. The addition of molasses reduced the ratio of fructose: glucose in the ensiled material and reduced the amount of mannitol produced during the ensilage process.

Chemical composition of cattle and buffalo spermatozoa and seminal plasma under different climatic conditions.

on the quality of buffalo semen compared with other cattle (Sinha, Gupta & Roy, 1966). Semen was collected from four Murrah buffalo and four Hariana bulls and the study was made during the seasons mentioned in Table 1. Immediately after collection, semen was stored in a thermos flask containing ice. The spermatozoa and seminal plasma were separated by centrifuging a known volume ofpooled semen at low temperature for halfan hour. The chemical constituents were determined according to the standard methods described by Hawk, Oser & Summerson (1954). The sodium content of the seminal plasma of the two species did not differ significantly, but seasonal differences were noted, indicating higher concentra¬ tions in cold, and slightly lower values in hot and hot-humid climates. The potassium and chloride contents of the seminal plasma and the potassium content of the buffalo spermatozoa were higher (P<0\m=.\01) than those of the bulls in all seasons. Steinbach & Dunham (1961) demonstrated that the motility of the sperma¬ tozoa of Arbacia punctulata depended upon the ion gradient (sodium and potas¬ sium) in the sperm cells. Cragle & Salisbury (1959) showed that potassium levels in diluting media, comparable to those found in seminal plasma, had an inhibitory effect on the oxygen consumption, fructose utilization and lactic acid accumulation of bull spermatozoa. These reports indicate that the higher potassium concentrations found in the seminal plasma as well as the sperma¬ tozoa of buffalo might, to some extent, be associated with the lower survival of these spermatozoa under storage conditions. The inorganic phosphorus and calcium contents of the seminal plasma of the two species did not differ significantly, nor did they differ significantly from

Regulation of sugar uptake by Aspergillus nidulans

Acetate inhibits the utilization of glucose or glycerol by cultures of Aspergillus nidulans but not of a mutant which lacks acetyl-CoA synthetase activity. The inhibition by acetate of the utilization of glucose, fructose, maltose, lactose, galactose, mannose, mannitol and glycerol was also demonstrated with a mutant of A . nidulans which lacks a component enzyme of the pyruvate dehydrogenase complex: in this mutant, the formation and excretion of pyruvate from the sugars was strongly inhibited by acetate, but occurred rapidly in its absence. In contrast, pyruvate formation from sucrose by this mutant was not inhibited by acetate, which indicates that the inhibitory action of acetate is on the uptake of the sugars by the cells. This was confirmed with washed suspensions of A . nidulans , which readily took up [U- 14 C]glucose and 2-deoxy-D-[U- 14 C]glucose, but not α -methyl-[U- 14 C] glucoside, from solutions thereof: acetate markedly inhibited these processes. Analysis of the materials extracted with hot water from cells exposed to 2-deoxy-D-[U- 14 C]glucose showed the glucose analogue to be predominantly present in a phosphorylated form at early times but not after more prolonged incubation; in the presence of acetate, the amounts of these labelled materials, but not their relative proportions, were markedly lowered.

Metabolism of Bovine Semen. XIX. Products of Fructose Metabolism by Washed Spermatozoa

The production of 14Co2 by washed bovine spermatozoa was determined in Krebs-Hensleit Ringer and in phosphate buffers with labeled fructose, glucose, and pyruvate as substrates. The 14C02 output from fructose and glucose was greater in Ringer, but for pyruvate it was greater in phosphate. With adenosine triphosphate in the Ringer buffer, fructose-6-phosphate, glucose-6-phosphate, and phosphoenolpyruvate were identifled as products of fructose-14C metabolism. Metabolic traps of unlabeled triose phosphates produced some increase in the accumulation of radioactive phosphate esters but did not result in the identification of additional intermediates. No differences between fructose-l-14C and fructose-6-14C were noted in the yield of 14C02 or in the identified nonvolatile products which included asparate, glutamate, lactate, citrate, fumarate, malate, and succinate. These data provide no reason to suspect deviation from the Embden-Meyerhof pathway and the citric acid cycle in utilization of fructose by bovine spermatozoa.

Carbohydrate utilization in the pre-ruminant calf.

1. Changes in blood sugar levels after giving carbohydrates have been used to assess carbohydrate utilization in pre-ruminant calves aged between 10 and 50 days.2. Glucose, galactose and lactose were readily utilized by all calves; the utilization of glucose and galactose increased with age, whereas that of lactose remained constant.3. Maltose and fructose utilization was low in young calves and increased slightly with age.4. Sucrose and starch were not utilized.5. Studies with three older pre-ruminant calves (aged 53, 88 and 106 days) in which the carbohydrates were infused into the proximal duodenum showed that glucose, galactose, lactose and xylose all caused marked increases in the level of blood reducing sugar, whereas fructose and sucrose caused no increase, and maltose was intermediate. Xylose and galactose caused very little change in the blood glucose concentration.6. It appeared that preferential uptake occurred of glucose from a glucose-galactose mixture.7. A non-linear relationship was found between the concentration of glucose or galactose infused and the increase in the level of blood reducing sugar.

Effects of deoxyfrenolicin on isolated adipose cells—I: Glucose and fructose utilization

Deoxyfrenolicin, at an optimal concentration of about 15 to 20 μg ml , stimulated to a greater extent than did insulin the oxidation of glucose and fructose, presumably via the pentose cycle, by isolated adipose cells. Stimulation of glucose uptake and lipogenesis from glucose and fructose were lower than by insulin, however. At a higher concentration (60 μg ml ) of deoxyfrenolicin, the stimulatory effects were reduced or abolished. Deoxyfrenolicin, at a suboptimal concentration (10.5 μg ml ), stimulated still further the maximally stimulated lipogenesis from glucose and fructose in response to insulin or several “insulin-like” proteases. It is suggested that deoxyfrenolicin stimulated sugar utilization in isolated adipose cells, at least in part, through a mechanism different from the actions of insulin or proteases.

Characterization and comparative studies of Streptomyces sp. 246 producing a cytostatic antibiotic.

The authors submit the results of taxonomic comparative studies of the strainStreptomyces sp. 246, which produces a polypeptide type cytostatic antibiotic. Strain 246 is characterized by tufts of straight sporophores of the “Rectus-Flexibilis” type, smooth spores arranged in chains (over 10 spores in a chain), yellow aerial and substrate mycelium, a negative test for melanin synthesis, utilization of glucose, arabinose, xylose, mannitol, fructose and rhamnose and inability to grow on sucrose, inositol, raffinose and cellulose. The taxonomic characters ofStreptomyces sp. 246 are identical with those of the strainStreptomyces chrysomallus JA 1449-1 and differ manifestly from those ofStreptomyces antibioticus strains (producing actinomycins, antimycin A and oleandomycin), fromStreptomyces cinereoruber ETH 7451 (producing rhodomycin) and from the strainStreptomyces sp. 4127 (producing actinomycin D).

On the utilization and renal excretion of fructose during the long-term intravenous administration

1. Vor der enzymatischen Bestimmung von Fructose wird Glucose mittels Glucoseoxydase zerstort, falls die zur Anwendung kommende Hexokinasepraparate Phosphoglucoisomerase enthalten.

Strain variations in the utilization of hexoses by Ehrlich ascites tumor cells.

1. 1. The utilization of glucose, fructose, mannose, galactose and glucosamine by six different strains of the Ehrlich ascites carcinoma was investigated. 2. 2. Considerable amounts of fructose were utilized by five of the strains. The sixth (strain W), however, converted fructose to lactic acid only to a very limited extent. In the latter strain chromatographic and enzymic methods revealed no metabolites of fructose, although the enzymes necessary for fructolysis could be detected. It is suggested that this was caused by restricted entry of fructose into these cells. 3. 3. Glucosamine is capable of penetrating the cells of all six strains. It results, as does glucose, in a depression of the cellullar oxygen consumption (Crabtree effect), although there is no evidence of a glycolytic degradation of this amino sugar. However, as demonstrated with strain W, phosphorylation of glucosamine and formation of intermediates of mucopolysaccharide and glycoprotein synthesis takes place. It is very likely that the inability to utilize glucosamine via the Embden-Meyerhof pathway is caused by too low an activity of glucosamine-6-phosphate deaminase. Nevertheless, depression of cellular respiration is observed, which indicates the primary importance of the phosphorylation step in the occurrence of this effect. 4. 4. It is shown that different strains of the Ehrlich ascites tumor may differ appreciably one from another in biochemical properties; this could explain conflicting results reported in the literature. It is also seen that comparative investigations of suitable strains may serve as a useful tool in solving problems of cellular metabolism.

Effects of Bacillus subtilis protease, type VIII (subtilopeptidase A) on isolated adipose cells Fructose utilization and its inhibition by avenaciolide, piericidin A and puromycin

1. 1. It was found that Bacillus subtilis protease, Type VIII (subtilopeptidase A, EC 3.4.4.16), like insulin, stimulated fructose utilization (oxidation and lipogenesis) by isolated adipose cells. The optimum concentration was comparable to the required for maximal stimulation of glucose utilization, about 5 μg/ml, and higher enzyme concentrations resulted in a reduced stimulation. Insulin and B. subtilis protease induced a higher υ max for the utilization of glucose and fructose. Insulin, but not B. subtilis protease, lowered the apparent K m values of either glucose or fructose utilization to about one half of the basal values. 2. 2. The basal and the elevated oxidation of fructose was not affected by palmitic acid, although its conversion to fatty acid was greatly reduced, and its conversion to glyceride-glycerol was stimulated. The protease, like insulin, reduced the oxidation of palmitic acid and enhanced its esterification in the presence of fructose. 3. 3. From the evidence obtained through the use of avenaciolide, piericidin A and puromycin, it is suggested that the basal and the insulin- or the protease-stimulated glucose and fructose uptake pathways may be different in isolated adipose cells, and that glucose and fructose uptake may again not be effected through identical mechanisms. Moreover, the kinetic data also suggested that B. subtilis protease stimulated glucose and fructose utilization by a mechanism quite distinct from that of insulin.

Effects of piericidin A on the metabolism of isolated adipose cells

The effects of piericidin A, a structural analog of coenzyme Q, on the metabolism of isolated adipose cells were studied. Piericidin A inhibited both the basal and the insulin-stimulated glucose and fructose utilization (oxidation and lipogenesis). Piericidin A completely abolished the stimulatory effects of proteases ( Bacillus subtilis protease, Streptomyces griseus protease and α-chymotrypsin) on glucose utilization. The utilization of palmitic acid was inhibited by piericidin A to a greater extent than amino acids. Piericidin A accelerated glycogenolysis, but exerted no significant effects on the level of lipid content or the oxidation of the cellular components. The lipolysis induced by lipolytic hormones (corticotropin and norepinephrine) or phosphodiesterase inhibitors (caffeine and theophylline) or by both was also blocked by piericidin A. The effects of peiricidin A on the isolated adipose cells were interpreted as probably being due to plasma membrane effects and possible effects on the adenyl cyclase system.

Utilization of fructose and glutamate by Rhodospirillum rubrum.

Fructose served as sole carbon source for the growth of Rhodospirillum rubrum anaerobically under light or aerobically in the dark while glucose did not. Glucose was not utilized by the organism at all. Radiorespirometric studies, using 14C specifically labelled fructose as substrate, revealed that fructose is catabolized exclusively via the Embden–Meyerhof–Parnas (EMP) glycolytic pathway. Both L-glutamic and D-glutamic acids can be utilized by this organism, via the tricarboxylic acid cycle (TCA) pathway, under either aerobic-dark or anaerobic-light conditions.

Uptake and oxidative utilization of glucose, fructose and galactose by rat mast cells

Uptake and oxidative utilization of glucose, fructose and galactose by rat mast cells

Utilization of some monosaccharides by two species of Colletotrichum.

Utilization of 8 monosaccharides, viz., glucose, fructose, galactose, mannose, sorbose, arabinose, xylose and rhamnose, by some plant pathogenic isolates ofColletotrichum gloeosphorioides andC. dematium has been studied with the help of paper chromatography. Among hexoses, the rate of utilization of glucose, fructose and mannose was fast, whereas, that of galactose was comparatively slow. The rate of assimilation of sorbose was very slow at early stages of incubation, although at later stages this rate showed marked enhancement. The pentoses were utilized readily. The dry weight of mycelial mats showed an increase up to the end of final incubation period (15 days), on sugars which were slowly assimilated. In cases where the sugars were consumed up rapidly, the dry weight at later stages of incubation either became nearly stationary or recorded slight fall.