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At least 19 recordsLinked to original sources
PubMed1977

Reactivity and inhibitor potential of hydroxycitrate isomers with citrate synthase, citrate lyase, and ATP citrate lyase.

The four isomers of hydroxycitrate have been tested as substrates and inhibitors for citrate synthase, citrate lyase, and ATP citrate lyase. None of the isomers served as a substrate for citrate synthase and they were moderate to weak inhibitors of this reaction. Of the four isomers, only (pncit)-(2S)-2-hydroxycitrate did not serve as a substrate for citrate lyase while (pncit)-(4S)-4-hydroxycitrate was the only isomer which did not serve as a substrate for ATP citrate lyase. No consistent pattern of reactivity or inhibitor potency was seen with the different isomeric hydroxycitrates. It is proposed that more than one mode of binding is possible between the isomers and the three different active sites.

ATP Citrate (pro-S)-Lyase↗
PubMed1979

The distribution of plasmids determining citrate utilization in citrate-positive variants of Escherichia coli from humans, domestic animals, feral birds and environments.

Sixty-seven isolates of citrate-positive variants of Escherichia coli were isolated from human, domestic animal, feral bird and environmental sources. With the exception of citrate utilization, all isolates were identified as typical E. coli by their biochemical reactions. The transmission of the ability to utilize citrate on Simmons' citrate agar was demonstrated in 53 (79.1%) out of the 67 citrate-positive E. coli variants obtained from various sources. Drug resistance determinants and citrate utilizing character were co-transmitted into E. coli K-12 by conjugation among citrate-positive E. coli isolates carrying R plasmids except for that isolated from horses. The other characters (haemolysin or colicin production, raffinose or sucrose fermentation) were not transmitted together with the citrate utilizing character. These facts suggested that the structural gene responsible for citrate utilizing ability in citrate-positive variants of E. coli was located on a conjugative plasmid.

Animals↗
PubMed1975

Studies on citrate metabolism in liver injuries. 1. Fasting blood citrate level in chronic hepatitis and liver cirrhosis.

For the purpose to study the citrate metabolism in liver diseases, blood citrate, blood glucose and serum non-esterified fatty acids (NEFA) in fasting state were measured in the subjects with chronic hepatitis and with liver cirrhosis. Citrate and glucose were measured by the enzymatic methods. NEFA was measured colorimetrically. Fasting blood citrate level was investigated in relation to the type and extent of these liver diseases. Results revealed the following: 1. Fasting blood citrate level rose with the severity of liver diseases, especially in decompensated liver cirrhosis. 2. No significant difference in fasting blood citrate level was found between the subjects with and without glucose intolerance. 3. Fasting blood citrate level had a closer correlation with serum NEFA level than with blood glucose level. From these results, it has been concluded that the increase in blood citrate level in liver diseases is due to the impaired uptake of citrate by the liver and the increased release of citrate from peripheral tissues.

Blood Glucose↗
PubMed1978

Whole blood storage in citrate and phosphate solutions containing half-strength trisodium citrate: cellular and biochemical studies.

The efficacy of whole blood preservation in acid citrate dextrose (ACD-A) and citrate-phosphate dextrose (CPD) anticoagulants containing half-strength trisodium citrate concentrations, was determined by biochemical and cellular assessment during 28 day storage at 4 degrees--6 degrees. Erythrocyte 2,3-DPG and ATP concentrations, serum potassium, plasma haemoglobin, and blood pH values were similar between the standard and half-strength citrate counterpart in both ACD-A and CPD series, throughout the entire storage period. Erythrocyte indices (MCV, MCH, MCHC, and osmotic fragility) and the red cell, platelet, and leucocyte counts, were also similar regardless of the final citrate concentration in both ACD-A and CPD series during the 28 day storage period. Tests of coagulation (PT, KCCT, TT, and ethanol gel) and fibrinogen levels were also similar, except for a lower quantity of clottable fibrinogen at day 28 in half-strength CPD. The formation of platelet and leucocyte aggregates during storage, as measured by changes in the SFP, were similar in magnitude whether or not the half-strength citrate formulation was used in ACD-A or CPD. Phagocytic and bactericidal capacity against Staph. aureus was normal following 24-hr storage at 4 degrees--6 degrees, in both ACD-A and CPD preserved blood, regardless of the final citrate concentration. It may now be concluded from this evaluation and those of others, that a reasonable argument can be made for reducing the citrate quantity presently used during blood storage, in order to provide a safe and effective transfusion product for routine use.

Adenosine Triphosphate↗
PubMed1975

Fluorometry of citrate in serum, with use of citrate (pro-3S)-lyase.

We describe a procedure for enzymatic assay of citrate in human serum. The citrate is degraded to acetate and oxaloacetate with citrate oxaloacetate-lyase (pro-3S-CH2-COO- yields acetate) (EC 4.1.3.6). Some oxaloacetate loses CO2 to form pyruvate. Addition of malate and lactate dehydrogenases (EC 1.1.1.37 and 1.1.1.27) permits determination of the oxaloacetate and pyruvate generated, and thus of the citrate concentration. The decrease in NADH concentration is measured fluorometrically. Results obtained for 30 consecutive human sera by this procedure were compared to the procedure in which the citrate is converted to pentabromoacetone. There was no statistically significant difference in values obtained by the two procedures. The range of values (mean plus or minus 2 SD) found for sera from 25 blood donors by this procedure was 12.8-27.2 mg/liter (mean, 19.0 mg/liter). Serum citrate as measured by both procedures during a glucose tolerance test was decreased from initial values under the influence of administered glucose (and endogenous insulin). Insulin concentrations were also measured during these glucose-tolerance tests. Citrate concentrations remain subnormal after the glucose and insulin concentrations return to their initial values. This accords with published reports.

Acetone↗
PubMed1975

Studies on citrate metabolism in liver injuries. 2. Response of liver citrate to glucose load.

The effect of glucose load on the levels of blood glucose, serum non-esterified fatty acids (NEFA) and liver citrate was investigated in carbontetrachloride-intoxicated (injured) rats and compared with non-intoxicated controls. The citrate level in the liver from injured animals showed 15-fold of the value of the control. Glucose load on these animals caused gradual decrease in the citrate level, whereas similar administration to the control caused inverse results. The serum NEFA levels were lowered by glucose load in both of injured and control animals. The pattern of changes in the citrate level after glucose load in the liver from injured animals was similar to that in the muscle from the control, suggesting a similarity on citrate metabolism between the injured liver and the muscle. The possible mechanisms for these results were discussed in relation to the difference in citrate metabolism between the liver and the muscle.

Animals↗
PubMed1976

[Behavior of some parameters of lipid and energy metabolism. 2. Activity of citrate synthase, ATP citrate lyase, fatty acid synthase, and glucose-6-phosphate dehydrogenase in liver of growing rats on diets differing in fat content].

In continuation of previous investigations, the authors studied the behaviour of the activities of certain enzymes (citrate synthase, adenosine triphosphate citrate lyase, fatty acid synthase and glucose-6-phosphate dehydrogenase) in the livers of growing rats on diets differing in fat content. A high-fat diet resulted in a reduction of the activities of fatty acid synthase, glucose-6-phosphate dehydrogenase and adenosine triphosphate citrate lyase, whereas the activity of citrate synthase increased, which is interpreted in the sense of an acceleration of the introduction of acetyl residues into the citrate cycle for the purpose of oxidative final degradation, and as a removal of acetyl CoA for the purpose of fatty acid synthesis.

ATP Citrate (pro-S)-Lyase↗
PubMed1978

[Whole-body retention studies of 167Tm-citrate.--Estimation of radiation dose to human from 167Tm-citrate--(author's transl)].

For the purpose of calculating absorbed dose to humans from 167Tm-citrate, the whole-body retention studies using 5 rats were carried out. Up to 40 days following intravenous injection of 167Tm-citrate, the whole-body counts were monitored with a animal counter. The whole-body retention curve was obtained with three exponentaial components. Namely, the 26% of the injected 167 Tm-citrate had a biological half-time of 3.4 hours, 12.5% had a biological half-time of 99 hours and 61.5% had a biological half-time of 106 days. These results indicate, that three components consist of the rapid clearance from the kidneys, the retention in the liver and other soft tissues with relatively long half-time and the retention in the bones with long half-time. Based on these biological data and the MIRD Committee method, the average dose estimates to the bone and whole-body from intravenous administration of 1 mCi 167Tm-citrate were 7.08 rads and 1.28 rads, respectively.

Animals↗
PubMed1977

[Whole-body retention studies of 169Yb-citrate.--Estimation of radiation dose to humans from 169Yb-citrate (author's transl)].

For purpose of the estimation of the radiation dose to humans from 169Yb-citrate, the whole-body retention studies using five rats were carried out. Following intravenous administration of 169Yb-citrate, the whole-body activity was monitored for 40 days by the animal counter. The whole-body retention curve consisted of three components: the first with a 3.6 hours effective half-time, the second with an 154 hours effective half-time and the third with a 29.9 days effective half-time. Therefore it was assumed that 32% of the administered 169Yb-citrate clears from the kidney with a short biologic half-time (3.6hours), 18% remains in the liver and other soft tissues with a relatively long biologic half-time (194 hours) and 50% remains in the bone with a long biologic half-time (850 days). Based on these biological data and the MIRD Committe method, the average dose to the bone and whole-body were 20.8 rads/mCi and 4.5 rads/mCi respectively.

Animals↗
PubMed1979

Haemodynamic consequences of citrate infusion in the anaesthetized dog: comparison between two citrate solutions and the influence of beta blockade.

We have compared the effects of a solution of acid--citrate--dextrose (ACD) with those of a solution of citrate--phosphate--dextrose (CPD), infused at equal rates, on blood calcium ion concentration and different indices of haemodynamic performance in 17 dogs. The influence of beta adrenergic blockade on these changes was examined. The effects of ACD and CPD were studied in five dogs and were similar. Peripheral vascular changes were the principal cause of arterial hypotension. In six dogs, propranolol 0.5 mg kg-1 intensified the hypocalcaemia-induced left ventricular dysfunction.

Animals↗
PubMed1975

Intracellular pH (pHi) of red cells stored in acid citrate dextrose medium. Effects of temperature and citrate anions.

The intracellular pH (pHi) of red cells stored in acid citrate dextrose (ACD) medium was estimated by the 5,5'-dimethyloxazoldine,-2,4-dione (DMO) method. The initial pHi at 4degrees was about 7.6 and was higher than the extracellular pH (pHe) at 4degrees. During storage, both pHi and pHe decreased, but the former was always higher than the latter and the former decreased more slowly than the latter. The high pHi of ACD blood was a results of the temperature at which the pHe and the pHi were measured (4degrees) and the presence of citrate anions in the medium, and could be explained by application of the Donnan-Gibbs equilibrium. ATP and 2,3-diphosphoglycerate (DPG) were well-maintained in heparinized blood when it was acidified and pHe and pHi at 4degrees were both about 7.4, which suggests that improvement of blood preservation may be attained by suitable adjustment of the pHi and pHe of the blood.

Adenosine Triphosphate↗
PubMed1976

Quantitative determination of piperazine citrate in piperazine citrate syrup USP.

An assay for piperazine citrate in Piperazine Citrate Syrup USP is described. The assay method is based on the formation of a complex of piperazine with an acid dye, bromothymol blue. The complex can be extracted with chloroform and measured spectrophotometrically. The method is accurate and requires only 15 minutes for analysis, compared to four to five hours by the USP method.

Hydrogen-Ion Concentration↗
PubMed1975

Effect of aeration and sodium on the metabolism of citrate by Klebsiella aerogenes.

Anaerobic growth of Klebsiella aerogenes NCDO 711 (NCTC 418) on citrate was dependent on the presence of Na+ in the medium, and fermentation of citrate was mediated via the fermentation pathway enzymes, citrate lyase and a Na+-dependent oxalacetate decarboxylase. This confirms the previous findings on strain NCTC 418. Growth under aerobic conditions was independent of Na+. The mean generation time for cells grown aerobically on either Na+ or K+ citrate medium was about 60 min, with a molar growth yield of about 40 g (dry weight) of cells per mol of citrate utilized. Citrate was apparently metabolized aerobically in both the Na+ and K+ citrate cells via the citric acid cycle, since cell extracts contained alpha-ketoglutarate dehydrogenase but not the citrate fermentation enzymes. The presence of theother enzymes of the citric acid cycle in K. aerogenes was shown in earlier studies. Under aerated conditions (no detectable oxygen tension in the culture), growth was faster on the Na+ citrate medium (mean generation time, 85 min) than on the K+ citrate medium (mean generation time, 120 min). Both cultures grew slower than under aerobic conditions, presumably because of oxygen limitation. Despite the faster growth rate, the molar growth yield of the aerated Na+ citrate culture was one-half that observed for the aerated K+ citrate culture. Citrate was metabolized via the citric acid cycle in cells grown in the K+ citrate medium under aerated conditions since alpha-ketoglutarate dehydrogenase, but not the fermentation enzymes, was detected in extracts prepared from these cells. Metabolism of citrate in the Na+ citrate medium under aerated conditions occurred via both the fermentation pathway (approximately 75 percent) and the citric acid cycle (about 25 percent), as evidenced by (i) the presence of the fermentation enzymes and alpha-ketoglutarate dehydrogenase in extracts of cells grown under these conditions, (ii) a molar growth yield which was intermediate between that obtained for anaerobic and aerated K+ citrate cultures, and (iii) the excretion of acetate, which also occurred in anaerobic cultures but not in aerated K+ citrate or aerobic cultures.

Acetates↗
PubMed1978

Induction of citrate synthase by aldosterone in the rat kidney.

The possible induction of renal citrate synthase (E.C. 4.1.3.7) by aldosterone was evaluated in the adrenalectomized rat. Three hours after administration of aldosterone (0.8 microgram/100 g body wt), renal cortical and medullary citrate synthase activity was significantly increased as reported previously by Kinne and Kirsten (Kinne, R., Kirsten, R. 1968. Pfleugers Arch. 300:244). In contrast, no change in this activity was detected in the renal papilla or the liver, under the same conditions. Kinetic analysis revealed that injection of aldosterone had no effect on the KmS for acetyl-CoA and oxalacetate but augmented Vmax of renal medullary citrate synthase activity by 40%. The aldosterone-dependent increase in medullary citrate synthase activity was proportionate to the associated increase in the quantity of antiserum (specific for citrate synthase) required for half-maximal immuno-precipitation. The possibility that aldosterone induced the synthesis of citrate synthase was evaluated in two sets of experiments. In the first set, adrenalectomized rats were injected intraperitoneally with either aldosterone (0.8 microgram/100 g body wt) or the diluent, and simultaneously with 3H or 35S methionine (500 muCi/rat). The isotopes were reversed in about half of the experiments. Three hours after the injection, renal citrate synthase was isolated by ATP-sepharose column chromatography and immuno-precipitation with the specific antiserum. Aldosterone augmented methionine incorporation into renal citrate synthase by 55% but had no effect on incorporation into the hepatic enzyme. In the second set, adrenalectomized rats were injected with either aldosterone (0.8 microcram/100 g body wt) or the diluent, the kidneys were removed 1 hr later and medullary slices were incubated in either 3H- or 35S-methionine at 20 degrees for 2 hr. Mitochondrial citrate synthase was isolated either by ATP-sepharose column chromatography and immuno-precipitation, or by polyacrylamide gel electrophoresis. Aldosterone increased methionine incorporation into the immuno-precipitates by 30% and into the enzyme peak resolved by polyacrylamide gel electrophoresis by 43%. The latter increase was eliminated by prior administration of either actinomycin D (70--80 microgram/100 g body wt) or spirolactone (SC-26304) (80 microgram/100 g body wt). An equimolar dose of dexamethasone (0.8 microgram/100 g body wt) had no effect on the isotope ratio associated with citrate synthase activity in the polyacrylamide gels.

Acetyl Coenzyme A↗
PubMed1977

Interactions of citrate synthases from osmoconforming and osmoregulating animals with salt: possible signs of molecular eco-adaptation?

This study considers differential sensitivity of citrate synthase (citrate oxaloacetatelyase [CoA acetylating]) EC 4.1.3.7. from an osmoconforming animal (sea anemone) and an osmoregulating animal (the pig) to salt. Attention is drawn to the fact that the osmoconforming sea anemone is in essence a sessile creature while the pig is readily mobile and able to change its ionic environment at will. It had been shown earlier that citrate synthase from another osmoconformer (oyster) is also not sensitive to ionic strength while citrate synthase from osmoregulating white shrimp is sensitive to increasing levels of salt. However, these enzymes are characteristically regulated by ATP and alpha-ketoglutarate. Both forms of citrate synthase are denatured by 6 M guanidine hydrochloride and are aided by salt levels in their refolding but the rate and extent of refolding of the osmoconformer citrate synthase are greater than those of the osmoregulator citrate synthase. Catalytic activity of both forms of citrate synthase is inhibited by incubation in distilled water; osmoconformer citrate synthase was inhibited completely in 7 h while osmoregulator citrate synthase was inhibited only 60% in this time and 80% after 22 h in distilled water. The eco-adaptive and evolutionary implications of these findings are discussed.

Adaptation, Physiological↗
PubMed1979

Plasmids in Escherichia coli controlling citrate-utilizing ability.

The citrate-utilizing ability of 19 out of 22 citrate-positive Escherichia coli strains isolated from pig sewage was transferred via conjugation to E. coli K-12. The conjugal transfer of citrate-utilizing (Cit) abilities was thermosensitive and concurrent with transfer of drug resistance. Weakly citrate-positive colonies were readily obtained in conjugation experiments. Their Cit characters could be transmitted to the other E. coli strains at a similar frequency in the retransfer experiments, and the transconjugants obtained still showed same characteristic growth on Simmons citrate agar plates. The 19 thermosensitive plasmids conferring citrate utilization and drug resistance were Fi-, and 16 of these plasmids belonged to incompatibility group H1. However, occasionally two conjugative plasmids (pOH3122-1 and pOH3124-1) carrying only the citrate utilization were also obtained in the conjugation experiments, and they were Fi+ and compatible with 19 reference R plasmids. In the two citrate-positive E. coli strains, it was suggested that the conjugative Cit plasmid showing Fi+ character and the more thermosensitive H1 plasmid conferring both the Cit character and drug resistance coexisted in the strain. The characterization of citrate utilization plasmids derived from pig farm sewage is discussed.

Animals↗
PubMed1975

Inactivation of citrate lyase from Rhodopseudomonas gelatinosa by a specific deacetylase and inhibition of this inactivation by L-(+1-glutamate.

A previously unrecognized enzyme, citrate lyase deacetylase, has been purified about 140-fold from cell extracts of Rhodopseudomonas gelatinosa. It catalyzed the conversion of enzymatically active acetyl-S-citrate lyase into the inactive HS-form and acetate. The enzyme exhibited an optimal rate of inactivation at pH 8.1. Because of the instability of acetyl-S-citrate lyase at acidic and alkaline pH values, all assays were carried out at pH 7.2, where the spontaneous hydrolysis of the acetyl-S-citrate lyase was negligible and deacetylase showed 70% of the activity at pH 8.1. The apparent Km value for citrate lyase was 10(-7) M at pH 7.2 and 30 C. The activity of the deacetylase was restricted to the citrate lyase from R. gelatinosa. The corresponding lyases from Enterobacter aerogenes (formerly Klebsiella aerogenes) and Streptococcus diacetilactis were not deacetylated; likewise, thioesters such as acetyl-S coenzyme A, acetoacetyl-S coenzyme A, and N-acetyl-S-acetyl-cysteamine were also not hydrolyzed. Citrate lyase deacetylase was present in very small amounts in cells of R. gelatinosa grown with acetate or succinate; it was induced by citrate along with the citrate lyase. L-(+)-Glutamate strongly inhibited the deacetylase. Fifty percent inhibition was obtained at a concentration of 1.4 X 10(-4) L-(+)-glutamate. D-(-)-Glutamate, alpha-ketoglutarate, L-alpha-hydroxyglutarate, L-(-)-proline, and other metabolites were less effective.

Acetates↗