ABSTRACT
In photorespiration, leaf peroxisomes convert serine to glycerate via serine-glyoxylate aminotransferase and NADH-hydroxypyruvate reductase. We isolated intact spinach leaf peroxisomes in 0.25 M sucrose, and characterized their enzymatic conversion of serine to glycerate using physiological concentrations of substrates and coenzymes. In the presence of glycolate (glyoxylate), and NADH and NAD alone or together in physiological proportions, the rate of serine-to-glycerate conversion was enhanced and sustained by the addition of malate. The rate was similar at 1 and 5 mM serine, but was two to three times higher in 50 mM than 5 mM malate. In the presence of NAD and malate, there was 1:1 stoichiometric formation of glycerate and oxaloacetate. Addition of 1 or 5 mM glutamate resulted in a negligible enhancement of the conversion of hydroxypyruvate to glycerate. Intact peroxisomes produced glycerate from either serine or hydroxypyruvate at a rate two times higher than osmotically lysed peroxisomes. These results suggest that under physiological conditions, the peroxisomal malate dehydrogenase operates independent of aspartate-alpha-ketoglutarate aminotransferase in supplying NADH for hydroxypyruvate reduction. This supply of NADH is the rate-limiting step in the conversion of serine to glycerate. The compartmentation of hydroxypyruvate reductase and malate dehydrogenase in the peroxisomes confers a higher efficiency in the supply of NADH for hydroxypyruvate reduction under a normal, high NAD/NADH ratio in the cytosol.
Subject(s)
Glyceric Acids/biosynthesis , Malate Dehydrogenase/metabolism , Microbodies/enzymology , Plants/enzymology , Serine/metabolism , NAD/metabolism , Oxidation-Reduction , Pyruvates/metabolismABSTRACT
The Calvin cycle of carbon dioxide fixation constitutes a biosynthetic pathway for the generation of (multi-carbon) intermediates of central metabolism from the one-carbon compound carbon dioxide. The product of this cycle can be used as a precursor for the synthesis of all components of cell material. Autotrophic carbon dioxide fixation is energetically expensive and it is therefore not surprising that in the various groups of autotrophic bacteria the operation of the cycle is under strict metabolic control. Synthesis of phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase, the two enzymes specifically involved in the Calvin cycle, is regulated via end-product repression. In this control phosphoenolpyruvate most likely has an alarmone function. Studies of the enzymes isolated from various sources have indicated that phosphoribulokinase is the target enzyme for the control of the rate of carbon dioxide fixation via the Calvin cycle through modulation of existing enzyme activity. In general, this enzyme is strongly activated by NADH, whereas AMP and phosphoenolpyruvate are effective inhibitors. Recent studies of phosphoribulokinase in Alcaligenes eutrophus suggest that this enzyme may also be regulated via covalent modification.
Subject(s)
Bacteria/metabolism , Carbon Dioxide/metabolism , Phosphotransferases (Alcohol Group Acceptor) , Bacteria/enzymology , Bacteria/growth & development , Glyceraldehyde 3-Phosphate/biosynthesis , Glyceric Acids/biosynthesis , Phosphotransferases/biosynthesis , Phosphotransferases/metabolism , Ribulose-Bisphosphate Carboxylase/biosynthesis , Ribulose-Bisphosphate Carboxylase/metabolism , Species SpecificitySubject(s)
Glyceric Acids/biosynthesis , Phosphotransferases (Alcohol Group Acceptor) , Veillonella/metabolism , Adenosine Triphosphate/metabolism , Alcohol Oxidoreductases/metabolism , Carbohydrate Dehydrogenases/metabolism , Carboxy-Lyases/metabolism , Coenzyme A Ligases/metabolism , Glyceric Acids/metabolism , Glyoxylates/metabolism , Isocitrate Lyase/metabolism , Oxo-Acid-Lyases/metabolism , Phosphotransferases/metabolismABSTRACT
The pathway of degradation of nitrilotriacetate (NTA) was determined by using cell-free extracts and a 35-fold purification of NTA monooxygenase. The first step in the breakdown was an oxidative cleavage of the tertiary amine by the monooxygenase to form the aldo acid, glyoxylate, and the secondary amine, iminodiacetate (IDA). NTA N-oxide acted as a substrate analog for induction of the monooxygenase and was slowly metabolized by the enzyme, but was not an intermediate in the pathway. No intermediate before IDA was found, but an unstable alpha-hydroxy-NTA intermediate was postulated. IDA did undergo cleavage in the presence of the purified monooxygenase to give glyoxylate and glycine, but was not metabolized in cell-free extracts. Glyoxylate was further metabolized by cell-free extracts to yield CO2 and glycerate or glycine, products also found from NTA metabolism. Of the three bacterial isolates in which the NTA pathway has been studied, two strains, one isolated from a British soil and ours from a Michigan soil, appear to be almost identical.
Subject(s)
Acetates/metabolism , Nitrilotriacetic Acid/metabolism , Pseudomonas/metabolism , Soil Microbiology , Biodegradation, Environmental , Carbon Dioxide/biosynthesis , Cell-Free System , Glyceric Acids/biosynthesis , Glycine/biosynthesis , Glyoxylates/metabolism , Oxygenases/metabolism , Pseudomonas/enzymologyABSTRACT
In livers from fasted rats perfused with bicarbonate buffer containing bovine albumin and erythrocytes, adrenalectomy decreased glycogen levels and glucose production, impaired the incorporation of 14C from [14C]lactate into glucose or glycogen, and decreased the activity of the active (I) form of glycogen synthase. Cortisol treatment restored gluconeogenesis after 1 h and glycogen synthesis after 2 h. Adrenalectomy did not alter the production of glucose or lactate or the levels of gluconeogenic intermediates in livers from fasted rats perfused with fructose, but reduced the formation of glycogen from this substrate. Adrenalectomy increased the levels of lactate and decreased the levels of P-pyruvate and subsequent intermediates in the gluconeogenic pathway. These changes were reversed by cortisol treatment. It is concluded that glucocorticoids support gluconeogenesis and glycogen synthesis in livers from fasted rats primarily by facilitating a reaction(s) located between pyruvate and P-pyruvate in the gluconeogenic pathway and by promoting the conversion of inactive to active glycogen synthase.
Subject(s)
Corticosterone/pharmacology , Gluconeogenesis/drug effects , Glucose/biosynthesis , Hydrocortisone/pharmacology , Liver Glycogen/biosynthesis , Liver/metabolism , Adenosine Diphosphate/metabolism , Adenosine Monophosphate/metabolism , Adenosine Triphosphate/metabolism , Adrenalectomy , Animals , Aspartic Acid/biosynthesis , Cyclic AMP/metabolism , Fasting , Fructose/metabolism , Glucosephosphates/biosynthesis , Glyceric Acids/biosynthesis , Glycogen Synthase/metabolism , Lactates/metabolism , Liver/enzymology , Liver Glycogen/metabolism , Male , Phosphorylases/metabolism , Pyruvates/biosynthesis , RatsSubject(s)
Myocardium/metabolism , NADP/metabolism , NAD/metabolism , Adenosine Monophosphate/analogs & derivatives , Adenosine Monophosphate/pharmacology , Animals , Cardiomegaly/enzymology , Cardiomegaly/metabolism , Cardiomegaly/pathology , Coenzyme A Ligases/antagonists & inhibitors , Coenzyme A Ligases/metabolism , Epinephrine , Glyceraldehyde-3-Phosphate Dehydrogenases/metabolism , Glyceric Acids/biosynthesis , Glycolysis , Hydrolases/metabolism , Myocarditis/chemically induced , Myocarditis/enzymology , Myocarditis/metabolism , Myocarditis/pathology , Myocardium/enzymology , Myocardium/pathology , NAD/biosynthesis , NAD/blood , NADP/biosynthesis , NADP/blood , Phosphotransferases/metabolismSubject(s)
Bacteria/metabolism , Bicarbonates/metabolism , Carboxy-Lyases/metabolism , Acetates/metabolism , Aspartic Acid/biosynthesis , Bacteria/enzymology , Carbon Radioisotopes , Ferredoxins , Glutamates/biosynthesis , Glyceric Acids/biosynthesis , Malate Dehydrogenase/metabolism , Pentosephosphates , Phosphates , Phosphoenolpyruvate Carboxykinase (GTP)/metabolism , Pyruvate Carboxylase/metabolism , Pyruvates , Sugar Phosphates/biosynthesis , Sulfides/metabolism , Thiosulfates/metabolismSubject(s)
Cyanobacteria/metabolism , Glycolates/metabolism , Alanine/biosynthesis , Alcohol Oxidoreductases/metabolism , Carbon Dioxide/biosynthesis , Carbon Radioisotopes , Carboxy-Lyases/metabolism , Cell-Free System , Cyanobacteria/enzymology , Darkness , Decarboxylation , Glyceric Acids/biosynthesis , Glycine/biosynthesis , Glyoxylates/biosynthesis , Glyoxylates/metabolism , Light , Malates/biosynthesis , Oxidation-Reduction , Oxidoreductases/metabolism , Oxo-Acid-Lyases/metabolism , Phosphotransferases/metabolism , Pyruvates/biosynthesis , Spectrophotometry , Transaminases/metabolism , Transferases/metabolismSubject(s)
Organoids/enzymology , Acyltransferases/analysis , Alcohol Oxidoreductases/analysis , Carnitine , Chloroplasts/enzymology , Fatty Acids/metabolism , Glyceric Acids/biosynthesis , Glycerolphosphate Dehydrogenase/analysis , Glycine/biosynthesis , Glycolates/metabolism , Glyoxylates/metabolism , Kidney/cytology , Kidney/enzymology , L-Lactate Dehydrogenase/analysis , Liver/cytology , Liver/enzymology , Malate Dehydrogenase/analysis , Malates/metabolism , Microbodies/enzymology , Plant Cells , Plants/enzymology , Serine/biosynthesisSubject(s)
Lactates/metabolism , Liver/metabolism , Pituitary Gland/physiology , Animals , Carbon Dioxide/metabolism , Carbon Isotopes , Citric Acid Cycle , Cyclic AMP/metabolism , Fasting , Fatty Acids/biosynthesis , Gluconeogenesis , Glucosephosphates/biosynthesis , Glyceric Acids/biosynthesis , Hypophysectomy , Kinetics , Liver Glycogen/biosynthesis , Male , Organophosphorus Compounds/biosynthesis , Oxidation-Reduction , Perfusion , Phosphoenolpyruvate/biosynthesis , Protein Biosynthesis , Pyruvates/biosynthesis , RatsSubject(s)
Fructose/metabolism , Glucose/metabolism , Glyceraldehyde/biosynthesis , Liver Glycogen/biosynthesis , Aldehyde Oxidoreductases/metabolism , Animals , Blood Glucose , Carbohydrate Epimerases/metabolism , Carbon Isotopes , Diaphragm/metabolism , Fructosephosphates , Glucose/analysis , Glucose-6-Phosphatase/metabolism , Glyceric Acids/biosynthesis , Mice , NAD , Pentosephosphates , Phosphotransferases/metabolism , Rats , Trioses , Tritium , Uridine Diphosphate Sugars/metabolismSubject(s)
Glycine/biosynthesis , Glycolates/biosynthesis , Oxygen Consumption , Plants/metabolism , Serine/biosynthesis , Alkaline Phosphatase , Carboxylic Acids/biosynthesis , Chromatography, Gas , Chromatography, Ion Exchange , Chromatography, Paper , Glyceric Acids/biosynthesis , Glycerophosphates/biosynthesis , Kinetics , Light , Oxygen Isotopes , Phosphoric Acids/biosynthesis , Phosphoric Acids/metabolism , Photosynthesis , Plants/radiation effects , Radiation EffectsSubject(s)
Glyceric Acids/metabolism , Hemoglobins/metabolism , Oxygen/metabolism , Acid-Base Equilibrium , Adaptation, Physiological , Anemia/metabolism , Anemia, Sickle Cell/metabolism , Binding Sites , Blood Preservation , Diphosphoglyceric Acids/metabolism , Erythrocytes/enzymology , Erythrocytes/metabolism , Erythropoiesis , Fetal Hemoglobin/metabolism , Glyceric Acids/biosynthesis , Hemoglobins, Abnormal/metabolism , Humans , Hypoxia/metabolism , Organophosphorus Compounds/biosynthesis , Organophosphorus Compounds/metabolism , Phosphates/metabolism , Phosphoglycerate Kinase/metabolism , Phosphotransferases/metabolism , Protein BindingSubject(s)
Fungi , Acids/analysis , Amino Acids/analysis , Amino Acids/metabolism , Carbohydrate Metabolism , Chromatography , Citrates/biosynthesis , Colorimetry , Culture Media , Electrophoresis , Fumarates/biosynthesis , Fungi/analysis , Fungi/classification , Fungi/cytology , Fungi/growth & development , Fungi/metabolism , Glyceric Acids/biosynthesis , Hydrogen-Ion Concentration , Lactates/biosynthesis , Light , Lipids/analysis , Malates/biosynthesis , Species Specificity , Spores/growth & development , Succinates/biosynthesis , TemperatureABSTRACT
Normal erythrocytes, when incubated with thyroid hormone, were found to have increased levels of 2,3-diphosphoglyceric acid. In addition, a partially purified enzyme preparation, when incubated with either a 1,3-diphosphoglyceric acid generating system or 1,3-diphosphoglyceric acid directly, showed increased levels of 2,3-diphosphoglyceric acid when exposed to thyroid hormone. The hormonal effect was biphasic and was witnessed after 5 min of incubation. Substitution on the 3 and 5 positions of the basic thyronine molecule was essential for hormonal effect. It appears that thyroid hormone acts by directly stimulating the diphosphoglycerate mutase enzyme. The hormonal effect on 2,3-DPG synthesis may offer a biochemical explanation for the shift in the oxyhemoglobin dissociation curve observed in thyroid disorders.
Subject(s)
Erythrocytes/metabolism , Glyceric Acids/biosynthesis , Phosphotransferases/metabolism , Thyroxine/pharmacology , Triiodothyronine/pharmacology , Adenosine Triphosphate/metabolism , Binding Sites , Glycolysis , Hemoglobins , Humans , Methods , Oxygen/blood , Oxygen Consumption , Phosphorus Isotopes , Time FactorsABSTRACT
A biphasic thyroid hormonal effect has been shown on 2,3-diphosphoglyceric acid synthesis in a crude enzyme, hemoglobin-free preparation from normal human erythrocytes.
Subject(s)
Erythrocytes/metabolism , Glyceric Acids/blood , Thyroxine/pharmacology , Triiodothyronine/pharmacology , Erythrocytes/drug effects , Erythrocytes/enzymology , Glyceric Acids/biosynthesis , Hemoglobins/metabolism , Humans , Phosphotransferases/metabolism , Stimulation, Chemical , Thyroid Diseases/blood , Thyroid Hormones/physiologyABSTRACT
Patients over 1 month of age with arterial oxygen pressures of less than 60 mm Hg were found to have elevated red cell 2,3-diphosphoglycerate (2,3-DPG) levels and blood with a decreased affinity for oxygen. The increase in 2,3-DPG was proportional to the degree of hypoxemia. In patients under 1 month of age this relationship was not observed. Red cells from adults, but not newborns, showed rapid increases in 2,3-DPG when incubated under nitrogen. Adult, but not fetal, deoxyhemoglobin was shown to facilitate in vitro synthesis of 2,3-DPG by binding this organic phosphate and relieving the product inhibition of 2,3-DPG mutase. Throughout a wide range change in oxygen affinity as measured by the P(50) is linear with respect to the 2,3-DPG concentration; a change of 430 mmumoles of 2,3-DPG/ml of red blood corpuscles (RBC) resulting in a change of the P(50) of 1 mm Hg. It appears that the 2,3-DPG of the adult's red cells responds rapidly to metabolic and environmental influences and in turn effects metabolism and the cellular environment. Many of these effects are not shared by the red cells of the newborn.