Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEXOSEPHOSPHATES”

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 181 records · Page 10Linked to original sources
PubMed1965

FACTORS AFFECTING HEPATIC GLYCOLYSIS AND SOME CHANGES THAT OCCUR DURING DEVELOPMENT.

1. Glycolysis by the supernatant fraction of homogenates of liver from guinea pigs and rats at various stages of development (foetal, newborn and adult) has been examined in a suitably fortified medium by measurement of inorganic phosphate uptake and production of lactate and glycerol 1-phosphate. 2. Starting with glucose as substrate, two rate-determining steps in glycolysis occur at the stages of glucose phosphorylation and the phosphofructokinase reaction in liver tissue from animals of all ages. Effects of the post-natal development of glucokinase are recorded. 3. The appearance of microsomal glucose 6-phosphatase activity around birth has an effect on glycolysis owing to competition for glucose 6-phosphate. 4. A stimulating effect of the nuclear fraction, especially from foetal liver, on glycolysis by the supernatant fraction is interpreted as being due to stimulation by adenosine-triphosphatase activity at the 3-phosphoglycerate-kinase stage.

Adenine Nucleotides↗
PubMed1965

EVIDENCE FOR EXTRACELLULAR ENZYMIC ACTIVITY OF THE ISOLATED PERFUSED RAT HEART.

1. The dissimilation of a number of externally added hexose phosphates and 5'-nucleotides by the perfused rat heart is described, and non-specific esterase and 5'-nucleotidase activity associated with the superficial cell membrane or vascular system has been demonstrated. 2. The rate of production of (14)CO(2) from [U-(14)C]glucose 6-phosphate suggests that oxidation occurred after hydrolysis to glucose. The incorporation of isotope from [U-(14)C]glucose 6-phosphate into glycogen was small, and similar to that obtained with [U-(14)C]glucose as substrate. 3. Glucose 6-phosphate was also partially isomerized to fructose 6-phosphate. Similarly, fructose 6-phosphate was converted mainly into glucose 6-phosphate, but also into glucose and inorganic phosphate. When fructose 1,6-diphosphate was added to the perfusate, a mixture of glucose 6-phosphate, fructose 6-phosphate and triose phosphates accumulated in the medium approximately in the equilibrium proportions of the phosphohexose-isomerase and triose phosphate-isomerase reactions, together with inorganic phosphate and some glucose. Glucose 1-phosphate was hydrolysed to glucose, but was not converted into glucose 6-phosphate. Leakage of enzymes out into the perfusion fluid did not occur. 4. This demonstration that phosphohexose isomerase, triose phosphate isomerase and aldolase may react with extracellular substrates at an appreciable rate suggests that these enzymes are attached to the cell membrane.

5'-Nucleotidase↗
PubMed1965

SOME PROPERTIES OF FRUCTOSE 1,6-DIPHOSPHATASE OF RAT LIVER AND THEIR RELATION TO THE CONTROL OF GLUCONEOGENESIS.

1. Fructose 1,6-diphosphatase has been purified tenfold from rat liver. The final preparation was not contaminated by either glucose 6-phosphatase or phosphofructokinase. The properties of the enzyme have been investigated in an attempt to define factors that could be of revelance to metabolic control of fructose 1,6-diphosphatase activity. 2. The metal ions Fe(2+), Fe(3+) and Zn(2+) inhibited the activity of fructose 1,6-diphosphatase even in the presence of an excess of mercaptoethanol; other metal ions tested had no effect. The inhibition produced by Zn(2+) was reversed by EDTA, but that produced by either Fe(2+) or Fe(3+) was not reversible. 4. The enzyme has a very low K(m) for fructose 1,6-diphosphate (2.0mum). Concentrations of fructose 1,6-diphosphate above 75mum inhibited the activity; however, even at very high fructose 1,6-diphosphate concentrations only 70% inhibition was obtained. 5. The activity was also inhibited by low concentrations of AMP, which lowered V(max.) and increased K(m) for fructose 1,6-diphosphate. Evidence is presented that suggests that AMP can be defined as an allosteric inhibitor of fructose 1,6-diphosphatase. 6. The inhibitions by both fructose 1,6-diphosphate and AMP were extremely specific. Also, the degree of inhibition was not affected by the presence of intermediates of glycolysis, of the tricarboxylic acid cycle, of amino acid metabolism or of fatty acid metabolism. 7. It is suggested that the intracellular concentrations of AMP and fructose 1,6-diphosphate could be of significance in controlling the activity of fructose 1,6-diphosphatase in the liver cell. The possible relationship between these intermediates and the control of gluconeogenesis is discussed.

Adenine Nucleotides↗
PubMed1965

PROPERTIES OF PHOSPHOFRUCTOKINASE FROM RAT LIVER AND THEIR RELATION TO THE CONTROL OF GLYCOLYSIS AND GLUCONEOGENESIS.

1. Phosphofructokinase from rat liver has been partially purified by ammonium sulphate precipitation so as to remove enzymes that interfere in one assay for phosphofructokinase. The properties of this enzyme were found to be similar to those of the same enzyme from other tissues (e.g. cardiac muscle, skeletal muscle and brain) that were previously investigated by other workers. 2. Low concentrations of ATP inhibited phosphofructokinase activity by decreasing the affinity of the enzyme for the other substrate, fructose 6-phosphate. Citrate, and other intermediates of the tricarboxylic acid cycle, also inhibited the activity of phosphofructokinase. 3. This inhibition was relieved by either AMP or fructose 1,6-diphosphate; however, higher concentrations of ATP decreased and finally removed the effect of these activators. 4. Ammonium sulphate protected the enzyme from inactivation, and increased the activity by relieving the inhibition due to ATP. The latter effect was similar to that of AMP. 5. Phosphofructokinase was found in the same cellular compartment as fructose 1,6-diphosphatase, namely the soluble cytoplasm. 6. The properties of phosphofructokinase and fructose 1,6-diphosphatase are compared and a theory is proposed that affords dual control of both enzymes in the liver. The relation of this to the control of glycolysis and gluconeogenesis is discussed.

Adenine Nucleotides↗
PubMed1965

CARP MYOGENS OF WHITE AND RED MUSCLES. GROSS ISOLATION ON SEPHADEX COLUMNS OF THE LOW-MOLECULAR-WEIGHT COMPONENTS AND EXAMINATION OF THEIR PARTICIPATION IN ANAEROBIC GLYCOGENOLYSIS.

1. The combined low-molecular-weight protein components of the myogens from carp white and red muscles [about 30% (w/w) of the myogen proteins] have been isolated by gel filtration on Sephadex G-75 columns. 2. The presence in this fraction from myogen of white muscle of the three main electrophoretic components previously isolated has been confirmed, and the low molecular weight of the fourth component has been definitely established. 3. The exclusive presence of this fourth component in the myogen of red muscle, apart from myoglobin, has also been demonstrated. 4. Glycogenolysis experiments in vitro have shown that the low-molecular-weight protein fraction from carp myogen does not contain enzymes from the Embden-Meyerhof chain.

Animals↗