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At least 19 recordsLinked to original sources
PubMed1977

Origin of alpha-glycerophosphate dehydrogenase isozymes in Drosophila melanogaster and their functional relationship in the alpha-glycerophosphate cycle.

The basis for the differentiation of L-glycerol-3-phosphate dehydrogenase (alpha-GPDH) into larval and adult isozymes in Drosophila melanogaster was investigated by the correlation of a lack of appearance of each isozyme during development within Drosophila bearing alpha-GPDH "null" alleles and by the study of a putative conversion factor. Conversion studies indicate the presence of a heat-labile RNase-resistant conversion factor present in crude larval extracts with the ability to convert GPDH-1 to GPDH-2 and GPDH-3 but not vice versa. In addition, "null" mutations at the Gpdh locus obliterate all isozymatic species of alpha-GPDH in all developmental stages. These observations suggest that all alpha-GPDH isozymes are the product of a single structural gene and that the multiple forms of this enzyme arise during successive developmental stages through an epigenetic modification of the primary Gpdh+ polypeptide. Finally, observations are reported which bear on the functional divergence of the alpha-glycerophosphate cycle in the adult and larval stage of development.

Alleles↗
PubMed1976

Regulation of alpha-glycerophosphate dehydrogenase activity in human term placental mitochondria.

1. alpha-Glycerophosphate dehydrogenase (sn-glycerol-3-phosphate:(acceptor) oxidoreductase, EC 1.1.99.5) activity in mitochondria isolated from human term placenta was found to be inhibited by ethyleneglycolbis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA). Addition of an excess of calcium ions to the incubation medium completely restored the original activity. The concentration of free calcium ion required to activate the alpha-glycerophosphate dehydrogenase was found to vary between 10 and 100 nM. 2. The pH optimum for alpha-glycerophosphate dehydrogenase activity varied with substrate concentration. The pH optima were 7.4 and 8.0 in the presence of 2 or 8 mM alpha-glycerophosphate, respectively. The apparent Km for alpha-glycerophosphate also varied with pH; the values being 0.4 mM at pH 7.05, 1.5 mM at pH 7.8, and 3.5 mM at pH 8.5. 3. alpha-Glycerophosphate dehydrogenase activity was inhibited by palmitoyl-CoA in a competitive manner with an apparent Ki value of about 10 muM. This inhibition was less pronounced in the presence of calcium or magnesium ions. 4. The activity of alpha-glycerophosphate dehydrogenase was inhibited by phosphoenolpyruvate, D- and DL-glyceraldehyde 3-phosphate and 3-phosphoglyceric acid, in a competitive manner, the apparent Ki values being 0.5, 0.95, 0.12 and 1.5 mM, respectively. 5. alpha-Glycerophosphate dehydrogenase activity in human placental mitochondria was found to be more sensitive to phosphoenolpyruvate, than the activity of the same enzyme in rat skeletal muscle mitochondria. alpha-Glycerophosphate dehydrogenase activity in rat brown adipose tissue mitochondria was only slightly affected by phosphenolpyruvate under the same conditions. 6. The data obtained suggest that the activity of alpha-glycerophosphate dehydrogenase in human placental mitochondria may be controlled by changes of the cytosolic level of palmitoyl-CoA, some glycolytic intermediates, and pH.

Adipose Tissue, Brown↗
PubMed1979

Purification and properties of L-alpha-glycerophosphate oxidase from Streptococcus faecium ATCC 12755.

A procedure was developed to purify the Streptococcus faecium ATCC 12755 L-alpha-glycerophosphate oxidase. The molecular weight of the purified enzyme was 131,000 and the subunit molecular weight was 72,000. Two moles of FAD were bound/mol of enzyme. Apo-L-alpha-glycerophosphate oxidase displayed physical properties similar to the holoenzyme as judged by electrophoresis in 10% buffer gels at pH 8.5 and by centrifugation in a 5 to 20% linear sucrose gradient. The apoenzyme was completely reactivated by incubation with FAD. L-alpha-Glycerophosphate oxidase was specific for L-alpha-glycerophosphate when compared with several other pohsphorylated glycerol and sugar derivatives. Oxygen was the preferred electron acceptor. At 10 mM DL-alpha-glycerophosphate (below the Km of 26 mM for L-alpha-glycerophosphate), activity was increased from 2.6- to 10-fold by increasing the buffer concentration from 0.01 to 0.1 m. This buffer effect was observed with potassium phosphate and other anionic buffers. In 0.001 m potassium phosphate buffer, pH 7.0, activity was increased by several divalent metal ions, including 10 mM CaCl2 (7.7-fold activation) and 10 mM MgCl, (6.8-fold activation). Fructose 6-phosphate and fructose1-phosphate were inhibitors of the L-alpha-glycerophosphate oxidase.

Cations, Divalent↗
PubMed1976

High activity of alpha-glycerophosphate oxidation by human placental mitochondria.

Human term placental mitochondria oxidize alpha-glycerophosphate at an unusually high rate as compared to other substrates. The apparent Km both for oxidation and alpha-glycerophosphate dehydrogenase (EC 1.1.99.5) activity of DL-alpha glycerophosphate determined in a medium containing 2mM EDTA and 5 mM MgSO4 was approx. 0.7 mM. EDTA inhibited the alpha-glycerophosphate oxidation if the later was used at low concentrations. A subsequent addition of MgSO4 or CaCl2 restored the original activity. EDTA had no effect on mitochondrial respiration at high concentration of alpha-glycerophosphate. Possible physiological role of relatively high activity of human placental mitochondrial alpha-glycerophosphate dehydrogenase is discussed.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1975

Acylation of carnitine and glycerophosphate in suspensions of rat liver mitochondria at varying levels of palmitate and coenzyme A.

Rates of acylation of carnitine and glycerophosphate in suspensions of isolated rat liver mitochondria were measured at varying levels of palmitate and coenzyme A in the presence of ATP. Addition of glycerophosphate caused considerable reduction in carnitine acylation at low, but not at high palmitate levels. Glycerophosphate acylation was less reduced by added carnitine. These results can be explained by a lower Km(acyl-CoA) in glycerophosphate acylation than in carnitine acylation. High levels of free coenzyme A caused inhibition of carnitine acylation, while the inhibitory effect of glycerophosphate acylation was small. Competition between palmitate and acyl-CoA for binding sites on protein (e.g., albumine added to the mitochondrial suspensions) was indicated by stimulation of carnitine acylation by palmitate with palmityl-CoA added as substrate in the absence of ATP. Refeeding a carbohydrate-rich diet to previously fasted rats resulted in increased glycerophosphate acylation and decreased carnitine acylation in isolated liver mitochondria.

Acylation↗
PubMed1977

Effects of chronic beta-glycerophosphate administration on growth rate and serum, liver and bile lipid composition in the rat--a toxicity study.

The possible toxic effects of a high dose of orally administered disodium beta-glycerophosphate to the rat for a period of 33 weeks has been investigated. The studies revealed taht beta-glycerophosphate administration had no effect on either survival rat, body weight, hematological and liver function tests or on serum and liver lipids concentrations. All organ weights were similar in the control and experimental rats excepts for the kidneys which were significantly heavier in the beta-glycerophosphate-fed rats. The biliary phospholipids concentrations was significantly increased in the treated group as observed previously during short-term treatments. Histological examination of liver and kidneys did not reveal any pathological findings. These results suggest that long-term administration of beta-glycerophosphate did not induce any toxic manifestations. The observed hyperplasia of the kidneys was attributed to the effect of the sodium content of beta-glycerophosphate.

Animals↗
PubMed1978

Role of dehydrogenase competition in metabloic regulation. The case of lactate and alpha-glycerophosphate dehydrogenases.

Many tissues expressing capacities for both anaerobic and aerobic glycolysis contain significant amounts of both lactate dehydrogenase and alpha-glycerophosphate dehydrogenase. Since the first serves in oxidation-reduction balance during anaerobic metabolism, while the second serves in the alpha-glycerophosphate cycle during aerobic metabolism, a provision seemed to be made (through competition for coenzyme) to encourage relatively exclusive function of either one or the other dehydrogenase. Competition for coenzyme was found to depend upon the isoenzyme form of each dehydrogenase (which determines the sensitivity of each reaction to modulators) and the concentration of two key metabolites, alpha-glycerophosphate and creatine phosphate, which differentially influence alpha-glycerophosphate dehydrogenases and lactate dehydrogenases. The sensitivities of various dehydrogenase isoenzymes to these modulators correlated well with their expected roles in the tissue of origin.

Animals↗
PubMed1992

Matrix mineralization in hypertrophic chondrocyte cultures. Beta glycerophosphate increases type X collagen messenger RNA and the specific activity of pp60c-src kinase.

The phenomenon of chondrocyte hypertrophy is accompanied by the expression of type X collagen and the appearance of matrix mineralization. These events are also associated with changes in the phosphorylation of intracellular proteins. In this study the addition of 10 mM beta-glycerophosphate to hypertrophic chondrocytes resulted in stimulation of type X collagen synthesis up to 10 days in culture and an increase in the expression of type X collagen mRNA. This was followed by the onset of mineralization and the appearance of calcium hydroxyapatite. In contrast, the addition of beta-glycerophosphate to non-hypertrophic chondrocytes failed to induce expression of type X collagen or to produce changes in calcium and phosphate. The increased formation of type X collagen and of mineral in hypertrophic chondrocytes was accompanied by changes in the tyrosine kinase pp60c-src. While the level of c-src protein decreased approximately 2.5-fold in hypertrophic chondrocytes after 17 days of beta-glycerophosphate treatment, the specific activity of pp60c-src kinase increased approximately 3-fold in the cells that could be induced to mineralize but remained unchanged in cells that did not exhibit this property. Regulation of kinase activity may be an important event in endochondral ossification.

Animals↗
PubMedDate not supplied

[Activity of various enzymes of the initial stages of glycerolipid biosynthesis and glycerophosphate content in alcoholic intoxication].

A distinct increase in activity of glycerokinase and glycerophosphate dehydrogenase and in content of L-alpha-glycerophosphate were observed in brain and liver tissues of rats treated with ethanol for 40 days. The similar alterations were observed after treatment with ehtanol for 80 days but in these conditions the content of L-alpha-glycerophosphate in liver tissue was decreased.

Alcoholic Intoxication↗
PubMed1979

Reconstruction of rat skeletal muscle glycerophosphate shuttle.

The activity of alpha-glycerophosphate shuttle in homogenate and in a reconstructed system (isolated mitochondria and cytoplasm) from rat skeletal muscle is presented. The influence of some inhibitors of mitochondrial alpha-glycerosphate dehydrogenase on the activity alpha-glycerophosphate shuttle is demonstrated. The possible operativity of alpha-glycerophosphate shuttle in skeletal muscle in vivo is discussed.

Animals↗
PubMed1978

Age-dependent alpha-glycerophosphate dehydrogenase activity changes in mutant and wild type Drosophila melanogaster.

The age-related changes in the activity of the extramitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPDH) were compared in two mutants of Drosophila melanogaster, a vestigial-winged and an alpha-glycerophosphate dehydrogenase deficient mutant with that of the wild type. The age-dependent patterns of activity change in both mutants were shown to be identical to that of the wild type. This is in spite of the lack of flight ability in both mutants, the reduced enzyme activity levels in the alpha-glycerophosphate mutant, and in the case of the vestigial flies, of reduced life-span. The results suggest that those mechanisms responsible for the observed aged-related activity changes in alpha-GPDH are intrinsically regulated, independent of functional flight, genetic alteration of specific activity, and life-span.

Age Factors↗
PubMed1979

Sequential changes in rat liver nuclear tri-iodothyronine receptors and mitochondrial alpha-glycerophosphate dehydrogenase activity after administration of tri-iodothyronine.

The dynamics of the induction of nuclear tri-iodothyronine receptors and mitochondrial alpha-glycerophosphate dehydrogenase were studied in rat liver after a single injection of tri-iodothyronine. The maximal binding capacity (C(max.)) and association constant (K(a)) of the nuclear receptors were determined by Scatchard analyses with and without correction for the endogenous tri-iodothyronine measured by radioimmunoassay. The administration of tri-iodothyronine induced sequential increases in the concentration of nuclear receptors and alpha-glycerophosphate dehydrogenase activity in the liver. The nuclear-receptor concentration was increased to 2.5 times that in the hypothyroid rat 1 day after the administration of hormone, and then decreased, with a half-life of about 2 days. alpha-Glycerophosphate dehydrogenase activity changed in parallel with the nuclear-receptor concentration, showing a delayed response. The total amount of non-histone protein in the liver was significantly increased 3 days after the administration. It seems likely therefore that the tri-iodothyronine-induced increase in nuclear-receptor concentration is responsible, at least in part, for the induction of this enzyme. The possibility is also suggested that nuclear receptors may be one of the non-histone proteins selectively synthesized at an early stage of the hormonal stimulation. Throughout the time course, the K(a) values of the nuclear receptors for tri-iodothyronine remained unchanged, when corrected for endogenous tri-iodothyronine bound to the non-histone proteins, although they were apparently changed when the correction was not made. The results obtained provide further evidence for hormonal modulation of the nuclear receptors which is closely linked with the hormonal effect.

Animals↗
PubMed1979

Cyanamide mediated synthesis under plausible primitive earth conditions. VI. The synthesis of glycerol and glycerophosphates.

The formation of glycerol occurs when a solution of DL-glyceraldehyde is heated in the presence of hydrogen sulfide at room temperature. DL-glyceraldehyde and dihydroxyacetone treated with hydrazine, as well as DL-glyceraldehyde incubated with formaldehyde are also partially converted to glycerol. The yields of the above reactions are from approximately 1% to about 3%. The formation of glycerophosphates occurs when glycerol is heated with ammonium dihydrogen phosphate and either urea or cyanamide. The yield of glycerophosphates is about 30%, most of which is sn-glycero-1 (3)-phosphate. These findings indicate that glycerol and sn-glycero-3-phosphate, which are moieties of glycerolipids, could have been formed under conditions which may have prevailed on the primitive Earth.

Biological Evolution↗
PubMed1978

Effects of chronic beta-glycerophosphate administration on growth rate and on serum, liver and bile lipid composition in the squirrel monkey--a toxicity study.

Oral administration of beta-glycerophosphate lowers the lithogenic index in patients with cholesterol gallstones and is considered to have potential for dissolving them. A high dose of beta-glycerphosphate was fed to primates (Squirrel monkeys) for a period of 15 months. There were no adverse effects on body weight, hematological or liver function tests. Serum, liver and bile lipids concentrations were not significantly changed, although serum and hepatic bile phospholipids were increased. Organ weights expressed as percent of body weight were not changed except for a slight increase in kidney weight. Histological examination of liver and kidneys did not reveal any pathological findings. Slight renal hypertrophy was attributed to the sodium content of beta-glycerophosphate.

Animals↗
PubMed1977

Partial purification of glycerophosphate acyltransferase from Escherichia coli.

Glycerophosphate acyltransferase, a membrane-bound enzyme catalyzing the initial step of phospholipid biosynthesis in Escherichia coli, has been extracted with Triton X-100, a nonionic detergent, and purified 20- to 40-fold. This preparation is free from lysophosphatidate acyltransferase. Glycerophosphate acyltransferase is inactive in detergent extracts, but can be reconstituted by the addition of phospholipid. Under such conditions, the enzyme is associated with phospholipid. The sole product of the reaction with acyl coenzyme A as substrate is 1-acyl-sn-glycero-3-phosphate. Furthermore, the enzyme shows a marked preference for saturated fatty acyl conenzyme A, implying that this enzyme is responsible for the predominance of saturated moieties in position 1 of E. coli phospholipids. Acyltransferase from two mutants, plsA and plsB, was partially purified and characterized. Results support the view that plsB is a structural gene for the acyltransferase, but suggest that the plsA gene product is not directly involved in phospholipid biosynthesis.

Acyltransferases↗