[Kinetics of Candida lipolytica yeast growth and biosynthesis of alpha-keto acids with thiamine deficiency in media with different carbon sources]

The growth kinetics of Candida lipolytica on glucose, acetate and hexadecane was studied in batch cultures at thiamine deficiency. The growth at the deceleration phase is of a linear character. The transition from the exponential phase to the linear one is accompanied with the accumulation of alpha-keto acids in the cultural broth, which is also observed in the stationary phase. The rate of acid production in the linear phase increases as the specific growth rate decreases, and reaches the maximum value in media with different carbon sources at mu = 0.01--0.06 h-1. Apparently, the deceleration of growth is due to a decrease in the activity of a thiamine-dependent enzyme (pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase or transketolase) which is a limiting point of biosynthetic processes. Here, a linear growth is determined by the constant activity of this enzyme per unit volume of the cultural broth which, in turn, depends on the constant concentration of the coenzyme, thiamine diphosphate, in the same volume.

Abnormal pyruvate and alpha-ketoglutarate dehydrogenase complexes in a patient with lactic acidemia

Activities of pyruvate decarboxylase (PDC), alpha-ketoglutarate decarboxylase (KGDC) and both the pyruvate and alpha-ketoglutarate dehydrogenase complexes (PDH complex and KGDH complex) were measured, and kinetic properties of PDC were studied in fibroblasts derived from normal individuals and from a 2-yr-old girl with congenital lactic acidemia and severe retardation of growth and development. The activities of PDC, KGDC, PDH complex, and KGDH complex in the patient were 1.12 +/- 0.12, 2.33 +/- 0.42, 9.00 +/- 0.50, and 16.46 +/- 1.57 and in controls 3.10 +/- 0.16, 5.36 +/- 0.56, 24.13 +/- 1.61 and 44.95 +/- 3.72 nmole/mg protein/hr. The optimum pH (6.0) and Michaelis constants (Km) for pyruvate of PDC (1.0-1.6 X 10(-5) M) were similar in fibroblasts of the patient and controls. PDC activity was more sensitive to denaturation by heat in the fibroblasts of the patient than those from controls, while heat denaturation curves of KGDC were similar in the patient and control. Higher concentrations of thiamine pyrophosphate (TPP) were required to protect PDC from heat denaturation in the patient. TPP was more easily removed from PDC in the patient than in the control by washing the fibroblasts with alkaline buffer. These results suggest that the PDC enzyme of the patient is in an altered molecular form, to which TPP is loosely bound. This particular constellation of abnormalities has not previously been reported in patients with lactic acidemia.

The measurement of coenzyme A and a coenzyme A-dependent enzyme. In microdissected epidermal material using coupled enzyme and bioluminescent reactions

A sensitive micromethod for the determination of Coenzyme A and its esters down to about 0.2 pmol in a volume of 10 microliters and of the activity of citrate synthase is outlined. Epidermal material from healthy and psoriatic skin was utilized in microgram quantity as tissue source. The assay utilizes the ketoglutarate dehydrogenase reaction to yield NADH on addition of free Coenzyme A and the subsequent measurement of NADH by a bioluminescent reaction with Acromobacter fischerii. The total Coenzyme A content in six healthy subjects measured in stratum Malpighii was 1.58 +/- 0.19 mmol per kg dry weight. In six psoriatic patients non-involved and involved epidermis contained 1.51 +/- 0.27 and 1.50 +/- 0.25 mmol/kg, respectively. Long-chain acyl-Coenzyme A comprised about 20% in lesion-free skin and 60% of total content in the involved psoriatic epidermis. The activity of citrate synthase in basal layers of healthy epidermis was 0.30 +/- 0.04 mkat/kg dry weight.

The effects of calcium ions and adenine nucleotides on the activity of pig heart 2-oxoglutarate dehydrogenase complex

1. The effects of Ca2+ (mainly by using EGTA buffers), pH, ATP and ADP on the activity of the 2-oxoglutarate dehydrogenase complex from pig heart were explored. 2. Ca2+ (about 30 micrometer) resulted in a decrease in the apparent Km for 2-oxoglutarate from 2.1 to 0.16 mM (at pH 7) without altering the maximal velocity. At 0.1 mM-oxoglutarate there was a 4--5-fold activation by Ca2+, with an apparent Km for Ca2+ of 1.2 micrometer. A similar activation was also observed with Sr2+ (Km 15.1 micrometer), but not wised markedly from pH 7.4 TO 6.6. The effects of Ca2+ remained evident over this pH range. 4. In the presence of Mg2+, ATP resulted in a marked increase in the apparent Km for oxoglutarate, whereas ADP greatly decreased thisp arameter. The concentrations of adenine nucleotide required for half-maximal effects were about 10 micrometer in each case. 5. The effects of the adenine nucleotides and Ca2+ on the apparent Km for oxoglutarate appeared to be essentially independent of each other, reversible, and demonstrable in the presence of end product inhibition by NADH and obtained. 6. Effects similar to those described above were also observed on the activity of 2-oxoglutarate dehydrogenase from rat heart and brown adipose tissue. 7. We discuss the mechanisms controlling this enzyme's activity and compare these regulatory features with those of NAD-isocitrate dehydrogenase and the pyruvate dehydrogenase system, which are also sensitive to Ca2+ and adenine nucleotides.

Friedreich ataxia. II. Normal kinetics of lipoamide dehydrogenase

Lipoamide dehydrogenase (LAD) kinetic values, Km and Vmax, were normal in 11 patients with Friedreich ataxia. Fibroblast activities of the pyruvate and alpha-ketoglutarate dehydrogenase complex, and LAD activities, were also normal. There was no reduction in oxidative decarboxylation of pyruvate, alpha-ketoglutarate, or several other substrates in intact fibroblasts. Methodologic differences may account for differences of opinion about putative abnormalities of the alpha-ketoacid dehydrogenase complexes.

[Regulation of alpha-ketoglutarate dehydrogenase complex from pigeon breast muscle]

The activity of alpha-ketoglutarate dehydrogenase complex from pigeon breast muscle is controlled by ADP and the reaction products, i. e. succinyl-CoA and NADH. ADP activates the alpha-ketoglutarate dehydrogenase component of the complex, whereas NADH inhibits alpha-ketoglutarate dehydrogenase and lipoyl dehydrogenase. In the presence of NADH the kinetic curve of the complex with respect to alpha-ketoglutarate and NAD and the dependence of upsilon versus [NAD] and upsilon versus [Lip (SH)2] in the lipoyl dehydrogenase reaction are S-shaped. In the absence of inhibitor ADP had no activating effect on lipoyl dehydrogenase; however, in the presence of NADH ADP decreases the cooperativity for NAD. The cooperative kinetics of the constituent enzymes of the complex are indicative of its allosteric properties. Isolation of the alpha-ketoglutarate dehydrogenase complex and its lipoyl dehydrogenase and alpha-ketoglutarate dehydrogenase components in a desensitized state confirms their allosteric nature. It is assumed that NADH effects of isolated alpha-ketoglutarate dehydrogenase is due to a shift in the equilibrium between different oligomeric forms of the enzyme.

[Alpha-ketoglutarate dehydrogenase activity of Candida lipolytica during alpha-ketoglutarate biosynthesis]

The activity of alpha-ketoglutarate dehydrogenase (KGDH) was assayed in cell-free yeast homogenates with respect to studying the mechanism of alpha-ketoglutarate (KG) overproduction by the thiamine-heterotrophic culture of Candida lipolytica in media with hexadecane. Two types of yeast cells were used for analysis: (1) cells grown in the conditions of thiamine excess (500 mcg/l) and taken at the logariphmic growth phase; (2) cells grown in the conditions of thiamine deficiency and taken at the beginning of KG overproduction when the cultural growth was limited by thiamine. The activity of KGDH was assayed in the absence of thiamine diphosphate (TDP) and in its presence, the content of the holoenzyme and the total content of the holoenzyme and the apoenzyme being determined respectively. The activity of holoKGDH in the thiamine-deficient cells of C. lipolytica producing KG was almost five times lower than in the cells grown in the conditions of thiamine excess. In the latter, all KGDH was in the form of the holoenzyme; in the thiamine-deficient cells, 90% of KDGH was in the form of the apoenzyme devoid of TDP and therefore lacking the enzyme activity. The total content of holoKGDH IN THE THIAMINE-DEFICIENt cells producing KG was twice as high as in the cells grown in the conditions of thiamine excess. The data obtained are discussed in relation with the mechanism of KG biosynthesis from n-alkanes by yeast cells.

[Activity of Krebs cycle oxidative enzymes in the brain in hypothermia]

Cooling of rats down to the rectal temperature of 33--35 degrees without the use of narcotic and neuroplegic drugs did not cause distinct alterations in activity of the oxidative enzymes of tricarboxylic acid cycle--isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, malate-, succinate- and pyruvate dehydrogenases in brain tissue. At the same time, inhibition of the activity of these dehydrogenases occurred in profound hypothermia (cooling to 19--20 degrees). In this case the activity of succinate dehydrogenase was decreased less distinctly as compared with the activity of NAD-dependent dehydrogenases. Succinic acid appears to be an especially important substrate for oxidation in brain of the chilled rats.

Genetic factors in Wernicke-Korsakoff syndrome

The authors study the role of thiamine-deficient diets in genetic variations contributing to Wernicke-Korsakoff syndrome.

The role of thiamine in nervous tissue

The possibility that thiamine (vitamin B1) has a role in nervous tissue that is independent of its well-documented coenzyme function is discussed. After reviewing the localization and metabolism of the vitamin and its phosphate esters, the effects of either thiamine deprivation or antimetabolites of thiamine on conduction and transmission, and the relationship between thiamine triphosphate and the genetic, neurological disease, subacute necrotizing encephalomyelopathy (Leigh's disease), it is suggested that despite the lack of hard evidence, it is likely that the vitamin possesses this alternate function.

[Antivitamin activity of thiaminase from B. thiaminolyticus with different routes of administration into animals]

Effect of bacterial thiaminase was studied in vivo after subcutaneous and intragastric administration of either the enzyme or of suspensions of intact and inactivated with an antibiotic bacterial cells, producing thiaminase. Activity of the thiamin-dependent enzymes (transketolase and alpha-ketoglutarate dehydrogenase) was distinctly decreased in liver and kidney tissues within 2 and 7 days after a single subcutaneous administration of 0.015 IU of the enzyme. Repeated administration of the enzyme within 4 days inhibited activity of thiamin-dependent enzymes in other tissues (heart, spleen, muscle and blood). Activity of thiamin-dependent enzymes in liver, kidney, heart, spleen, brain, muscles and blood was decreased more distinctly after administration of intact bacterial cells into mice stomach as compared to the effect of inactivated cells. Old animals were more sensitive to administration of intact bacterial cells than the young ones. The data obtained suggest that, besides the known thiamin-degrading effect of bacterial thiaminase in the intestinal contents, the enzyme exhibits functional activity within the animal tissues after the parenteral administration.

alpha-Ketoglutarate dehydrogenase mutant of Rhizobium meliloti

A mutant of Rhizobium meliloti selected as unable to grow on L-arabinose also failed to grow on acetate or pyruvate. It grew, but slower than the parental strain, on many other carbon sources. Assay showed it to lack alpha-ketoglutarate dehydrogenase (kgd) activity, and revertants of normal growth phenotype contained the activity again. Other enzymes of the tricarboxylic acid cycle and of the glyoxylate cycle were present in both mutant and parent strains. Enzymes of pyruvate metabolism were also assayed. L-Arabinose degradation in R. meliloti was found to differ from the known pathway in R. japonicum, since the former strain lacked 2-keto-o-deoxy-L-arabonate aldolase but contained alpha-ketoglutarate semialdehyde dehydrogenase; thus, it is likely that R. meliloti has the L-arabinose pathway leading to alpha-ketoglutarate rather than the one to glycolaldehyde and pyruvate. This finding accounts for the L-arabinose negativity of the mutant. Resting cells of the mutant were able to metabolize the three substrates which did not allow growth.

Pyruvate dehydrogenase deficiency in spinocerebellar degenerations

To study the incidence of abnormalities of the pyruvate (PDH) or ketoglutarate (KGDH) dehydrogenase complexes in patients with spinocerebellar degenerations, we measured the activities of PDH and KGDH in platelet-enriched preparations from the blood of 14 patients. Low PDH was found in 6 of the 14 patients; low KGDH was found in 2 of the 6. PDH-normal and PDH-abnormal patients could not be distinguished by clinical criteria. These results extend previous studies, which suggested abnormalities of pyruvate oxidation in patients with hereditary ataxias. The data imply that deficient activity of the PDH complex may be associated with spinocerebellar degenerations, and that the clinical phenotypes of the inherited ataxias can be associated with several genotypes.

[Kinetic properties of the alpha-ketoglutarate dehydrogenase complex from pigeon breast muscle]

A complex kinetic behaviour of the alpha-ketoglutarate dehydrogenase component isolated from the pigeon breast muscle alpha-ketoglutarate dehydrogenase complex was established. The dependence curve of the reaction rate versus substrate concentration has an intermediate plateau and a maximum. The shape of the kinetic curve and specific activity depend on the enzyme concentration both in the reaction mixture and in the original solution of enzyme. The kinetic pattern of isolated alpha-ketoglutarate dehydrogenase suggests that the enzyme is a multi-step dissociating system characterized by different rates of oligomeric forms interconversions at various steps of dissociation. It is assumed that the process of alpha-ketoglutarate dehydrogenase oligomerization is a cooperative one. The kinetic behaviour of the complex and its constituent alpha-ketoglutarate dehydrogenase component is characterized by the same type of the v + [S] dependence curves as is the isolated enzyme. The correlation between the kinetic properties of the enzyme complex and its alpha-ketoglutarate dehydrogenase component and the kinetic behaviour of free alpha-ketoglutarate dehydrogenase suggest that the association-dissociation processes which are probably typical for the component within the complex determine the kinetic behaviour of the complex to a large extent. It is assumed that the anomalous kinetic behaviour of the alpha-ketoglutarate dehydrogenase component is due to the cooperative effects during substrate binding, which are mediated by a shift in the equilibrium between the oligomeric forms of enzyme.

Kinetic evidence for a structural abnormality of lipoamide dehydrogenase in two patients with Friedreich ataxia

Two unrelated patients with Friedreich ataxia were deficient in the activity of the enzyme lipoamide dehydrogenase (LAD). The enzymes from the patients' platelets differed significantly from controls in activity, in KM for lipoamide, and in KM for NADH. The data are consistent with a structural mutation of the gene coding for LAD.

Pyruvate and citrate metabolism in the muscle tissue of Ascaris lumbricoides

Aconitase and NAD linked isocitrate dehydrogenase were present in Ascaris lumbricoides muscle at only very low activities, whilst there were significant levels of citrate synthase, NADP linked isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase and succinic thiokinase. Pyruvate dehydrogenase was present in A. lumbricoides muscle at levels comparable with mammalian tissues and results suggest that it is modulated via a phosphotransferase/phosphatase system. The tricarboxylic acid cycle intermediates, citrate, isocitrate and 2-oxoglutarate were all detected in freeze clamped muscle, but their steady state levels were considerably lower than those found in mammalian tissues.

[Histochemical study of the chemoreceptor function of the carotid body in comparison with the superior cervical ganglion]

The distribution and relative activities of some dehydrogenases and diaphorases in the rat's carotid body and ganglion cervicale superior were studied histochemically and cytophotometrically. The treatment of rats by the medium with decreased oxygen and increased carbon dioxide contents, a reliable rise of NAD--diaphorase activities was found in the interlobe tissue and (less expressed and late appearing) in the principal cells. In contrast, such changes were not observed in the ganglion cervicale superioir, that have not a special chemoreceptory function. It is supposed that these changes in enzyme activities in the carotid body is due to the chemoreceptory function of the intralobe tissue containing the IInd type cells and "special" cells of sensitive nerve terminals.

Biochemical effects of mercury poisoning in rats

Acute HgCl2 poisoning was shown to decrease significantly the pyruvate dehydrogenase (PyDH) and alpha-ketoglutanic dehydrogenese (alphaKgDH) activity in the kidney and liver but not in the brain. Rats receiving 77% of the 2 hr 50% lethal dose showed 57% of normal renal PyDH activity and 69% of normal renal alphaKgDH activity. Chronic Hg Cl2 poisoning resulted in an unexpected increase in PyDH and alphaKgDH activity in the kidneys where mercury was most concentrated. In acute methyl mercury injection, no significant effect on PyDH or alpha KgDH activities was observed after 2 days. Less mercury was accumulated in the tissues with methyl mercury poisoning than in the other treatments.

[Lactate dehydrogenase and Krebs cycle enzyme activity in rat liver during the growth of transplanted and spontaneous tumors]

Certain distinctions in the mouse and rat liver responses to transplanted and spontaneous tumours have been discovered at the initial periods of their growth. The most pronounced changes (the mosaic distribution of enzymatic activity in the lobe) are observed in the case of spontaneous tumours. Activities the Krebs cycle enzymes, especially of NAD-dependent enzymes are seen inhibited in the tumour-bearing liver at the terminal periods of growth of both spontaneous and transplanted tumours; lactate dehydrogenase activity increases (with the exception of mitochondrial lactate dehydrogenase in the rat liver with transplanted sarcomas).

Determination of pyruvate oxidation rate and citric acid cycle activity in intact human leukocytes and fibroblasts

We measured pyruvate oxidation in intact leukocytes and fibroblasts by measuring 14C02 production. The optimal pyruvate concentration appeared to be higher than that usually applied. Activities remained constant during the incubation and were proportional to the amount of tissue protein added. Man values (+/-SD) were 2.8 +/- 0.9 nmol/h per 10(6) cells and 37 +/- 14 nmol/h per mg of protein for leukocytes and fibroblasts, respectively, for [1-14C]pyruvate oxidation; and 2.1 +/- 0.8 nmol/h per 10(6) cells and 18 +/- 7 nmol/h per mg of protein, respectively for [2-14C]pyruvate oxidation. We compared oxidation rates of pyruvate and 2-oxoglutarate by intact cells with those of isolated mitochondria. The ratio of 14CO2 production vs. activity of mitochondrial marker enzyme demonstrated that the rate of pyruvate oxidation can adequately be assayed in intact cells, but that the permeability of the cell membrane is rate-limiting in the oxidation of 2-oxoglutarate. No significant oxidation of other intermediates of the citric acid cycle was found, presumably owing to a low rate of transport of these substances across the cell membrane.