The regulation of respiration during the assimilation of nitrogen in <i>Torulopsis utilis</i>

Yemm, E. W.; Folkes, B. F.

doi:10.1042/bj0570495

Cited by 41 publications

(29 citation statements)

References 22 publications

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“…By analogy with yeast (Yemm and Folkes, 1954) and higher plants, it was suggested that glutamine arises by the formation and subsequent amidation of glutamic acid. This compound is closely related to a-ketoglutaric acid, a key intermediate of the tricarboxylic acid cycle.…”

Section: Introductionmentioning

confidence: 99%

THE UTILIZATION OF ACETATE BY NEOCOSMOSPORA VASINFECTA

Budd

1966

New Phytologist

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Summary Mycelium of Neocosmospora vasinfecta, harvested during active growth, was incubated for up to 10 minutes in dilute solutions of [1‐14C]acetate or [2‐14C]acetate. Radioactivity in the respiratory CO2 and in identifiable compounds extracted from the mycelium was measured. Closely similar results were obtained with both [1‐14C]acetate and [2‐14C]acetate except for the loss of radioactivity to CO2, which took place much more rapidly from the [1‐14C]acetate. Water‐soluble compounds accounted for over 80% of the radioactivity of the mycelium. With incubation periods of up to 2.5 minutes, most of the radioactivity in the water‐soluble material was associated with organic acids, whereas with longer incubation, the label in basic compounds predominated, Glutamate was consistently the most heavily labelled basic compound, with small amounts of radioactivity in glutamine and aspartic acid. Radioactivity in the organic acid fraction was practically confined to citric acid after 2.5 minutes incubation; succinic, malic and other acids were significantly labelled after 10 minutes. The specific activities of these acids after 10 minutes decreased in the order citrate, succinate, malate, suggesting their involvement in the tricarboxylic acid cycle. The results are discussed in relation to the importance of the tricarboxylic acid cycle in acetate utilization, nitrogen assimilation and respiration.

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Section: Introductionmentioning

confidence: 99%

THE UTILIZATION OF ACETATE BY NEOCOSMOSPORA VASINFECTA

Budd

1966

New Phytologist

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“…Although glutamate does not initiate growth within the first 3 days, it does stimulate growth in this time period in the presence of a limiting amount of succinate (Table 8). Yemm & Folkes (1954) showed that nitrogen-deficient cultures of Torulopsis utilis, suspended under aerobic conditions in a carbohydrate-free medium, doubled or tripled their rate of oxygen uptake on the addition of ammonium nitrogen. Since this appeared to be a method of studying the systems of Recorded total pg.…”

Section: Oeidation Studiesmentioning

confidence: 99%

The Nature of the Lesion in the Succinate-requiring Mutants of Neurospora crassa: Interaction between Carbohydrate and Nitrogen Metabolism

Strauss

1956

Journal of General Microbiology

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SUMMARY: Mutants of Neurospora crmsa requiring dicarboxylic acids for an immediate growth response (SUC and at suc) oxidize acetate, and are inhibited by fluoroacetate with consequent citric acid accumulation to approximately the same extent as the wild-type. The concentration of nitrogen (as ammonium and nitrate salts) present in the conventional growth medium is inhibitory to the growth of these mutants and leads to an accumulation of acetylmethylcarbinol, pyruvic acid and a-ketoisovaleric acid. This inhibition is reduced and growth is stimulated by the addition of dicarboxylic acids or by diminution of the nitrogen present in 'minimal' medium. The addition of nitrogen salts to SUC mutants probably diverts dicarboxylic acids (already in short supply) from the catalysis of the oxidation of C, fragments via the tricarboxylic acid cycle to other reactions. This effect of nitrogen salts upsets the already precarious dicarboxylic acid balance of the suc mutants leading to a growth requirement and to the accumulation of intermediates.This investigation was begun because the existence of mutants of the ascomycete Neurospora crassa, which grow on minimal medium only after the addition of small quantities of dicarboxylic acids (succinate-requiring mutants), seemed difficult to reconcile with an apparent use of the tricarboxylic acid cycle for both synthesis and energy by Nearospora spp. (Lewis, 1948;Strauss, 1955a). Accepting the idea of a 'genetic block' in the cyclic metabolism of dicarboxylic acids by the succinate-requiring mutants seems to require the assumption that acetate is oxidized by some mechanism other than the tricarboxylic acid cycle (Krebs, Gurin & Eggleston, 1952) or that the 'genetic block' is not absolute. Since either of these explanations would be of interest, the properties of the succinate-requiring mutants have been studied in some detail.It now appears that the succinate-requiring mutants do use the tricarboxylic acid cycle, and that there is no enzymic block to the operation of the cycle. Dicarboxylic acids required to catalyse acetate oxidation are in short supply and, as a result, excess ammonium or nitrate nitrogen inhibits these mutants by withdrawing this limited supply of dicarboxylic acids for synthetic purposes. Inhibition by excess nitrogen is at least partly responsible for the failure of succinate-requiring mutants to grow normally on ' minimal medium' (Beadle & Tatum, 1945).It is the purpose of this paper to present the evidence for the interaction of carbohydrate and nitrogen metabolism in the succinate-requiring mutants, and to discuss briefly the implications of these findings.

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“…The organism used was Candida utilis NCYC737; this culture is derived from a single cell isolate from the strain ~~6 0 used in earlier studies by Yemm & Folkes (1954) and Sims & Folkes (1964).…”

Section: Organismmentioning

confidence: 99%

The Significance of Amino Acid Inhibition of NADP-linked Glutamate Dehydrogenase in the Physiological Control of Glutamate Synthesis in Candida utilis

Folkes

Sims

1974

Journal of General Microbiology

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SUMMARYIsotopic nitrogen (15N) was used to measure the rate of synthesis of glutamic acid and of glutamine in turbidostat cultures of Candida utilis grown on ammonium phosphate as N source.Steady-state experiments revealed that glutamic acid exists in more than one metabolic pool; approximately 5 % of the free amino acid is in a separate 'storage' pool while a small but measurable component is apparently in a separate pool used specifically for the synthesis of glutamine. Over the temperature range 15 to 25 "C the proportion of total nitrogen assimilated through glutamate was constant at 75 yo ; I 2 to I 5 yo entered cellular metabolism through glutamine amide. Decrease of ammonium levels in the culture medium resulted in slightly lower growth rates and a decreased size of glutamate pool, but the proportion of nitrogen assimilated through glutamate remained constant. Steady-state conditions could be disturbed by withholding nitrogen for a short period (10 to 20min) or by rapid shift of temperature. In both cases transient changes in growth rate, amino acid pools and rate of synthesis of glutamate and glutamine occurred. The rate of glutamate synthesis was very closely correlated with the size of the total pool of amino acids, and in vitro experiments confirmed that amino compounds were allosteric inhibitors of NADP-glutamate dehydrogenase. The in vivo data yielded a Hill number of 8, indicative of the very sharp inhibition occurring over the range 0.15 to 0.25 M-amino acids. For extracted enzyme preparations the Hill number was smaller (2 to 6 ) ; this may imply partial dissociation at the lower protein concentrations used for in vitro experiments.Analyses of organisms grown under steady-state conditions at various temperatures revealed that the amino acid feedback control on glutamate dehydrogenase is probably the chief mechanism involved in the regulation of glutamate synthesis to match growth requirements at different temperatures. Other physiological conditions in which glutamate formation is controlled are briefly discussed. I N T R O D U C T I O NIn earlier studies on food yeast (Candida utilis) we showed from measurements of rates of incorporation of 15N into amino acids that the synthesis of glutamic acid was the only route in this organism by which amino compounds were formed from inorganic nitrogen (Sims & Folkes, 1964). Furthermore, the kinetics of labelling of glutamic acid revealed that the enzymic reactions involved were not freely reversible within the cellular environment, since any appreciable rate of back reaction would have led to rates of isotope incorporation far in excess of those observed. The measured rates of labelling of most amino acids indicated rates of synthesis very close to those calculated to be necessary to sustain the observed rate * We dedicate this paper to Professor E. W. Yemm, who retires in 1974.

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The regulation of respiration during the assimilation of nitrogen in Torulopsis utilis

Cited by 41 publications

References 22 publications

THE UTILIZATION OF ACETATE BY NEOCOSMOSPORA VASINFECTA

THE UTILIZATION OF ACETATE BY NEOCOSMOSPORA VASINFECTA

The Nature of the Lesion in the Succinate-requiring Mutants of Neurospora crassa: Interaction between Carbohydrate and Nitrogen Metabolism

The Significance of Amino Acid Inhibition of NADP-linked Glutamate Dehydrogenase in the Physiological Control of Glutamate Synthesis in Candida utilis

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