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S. Dagley

Bio: S. Dagley is an academic researcher from University of Leeds. The author has contributed to research in topics: Bacterial oxidation & Citric acid cycle. The author has an hindex of 4, co-authored 4 publications receiving 159 citations.

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TL;DR: Adaptive patterns for a vibrio indicate that the oxidation of phenylalanine to homogentisic acid by this organism may proceed by two different pathways, one through phenylpyruvic and phenylacetic acids and the other through tyrosine and p-hydroxyphenyl pyruvic acid.
Abstract: SUMMARY: Adaptive patterns for a vibrio indicate that the oxidation of phenylalanine to homogentisic acid by this organism may proceed by two different pathways, one through phenylpyruvic and phenylacetic acids and the other through tyrosine and p-hydroxyphenylpyruvic acid. That the former pathway is used is confirmed by the isolation from metabolism fluids of the phenylhydrazone of phenylpyruvic acid. The vibrio does not appear to oxidize the side chains of phenylpropionic and phenylacetic acids before ring fission. The influence of cell suspension density on rates of oxidation of various highly polar compounds which may penetrate slowly into the cells has been studied.

78 citations

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TL;DR: Since it is established that mandelic acid and certain other aromatic compounds give rise to,-ketoadipic acid, the production of keto acids in phenylacetate metabolism is investigated, and kinetic investigations over a period of time defined by the position of the concentration maximlum are conducted.
Abstract: The bacterial oxidation of aromatic compounds closely related in chemical structure may proceed by different pathways. Thus, while the main features of the breakdown of mandelic acid are established, those of phenylacetate are not, except insofar as it is known to follow a different route (Stanier, 1950). The divergencies may possibly indicate a difference in the mode of ring fission; and since it is established that mandelic acid and certain other aromatic compounds give rise to ,-ketoadipic acid (Kilby, 1948, 1951; Stanier, 1950), we have investigated the production of keto acids in phenylacetate metabolism. At the same time we have attempted to determine whether the reactions of the tricarboxylic acid cycle play a part in these oxidations, and whether there is any evidence under favorable conditions for an abridged cycle as postulated by Barron, Ardao, and Hearon (1950) for Corynebacterium creatinovorans and termed by them the \"dicarboxylic acid cycle\". Pyruvic acid accumulates in aerated cultures of Aerobacter aerogenes growing on glucose or various dicarboxylic acids only when its rate of production exceeds the demands of logarithmic growth, while shortly after cell division ceases its presence may no longer be detected (Dagley et al., 1951). Since conditions in a growing or fully grown culture may not favor detection of metabolic intermediates, we have followed keto acid production by nonproliferating suspensions aerated in media from which the source of nitrogen has been omitted. Under such conditions the concentration of keto acids in the medium rises initially, attains a maximum, and then declines eventually to zero when the rate of decomposition exceeds the rate of formation. In studies of keto acid production, therefore, it is essential to conduct kinetic investigations over a period of time defined by the position of the concentration maximlum.

42 citations

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TL;DR: Krebs (1950) has drawn attention to the possibility that the dissimilation of citrate to oxalacetate and acetate may be a reversal of the synthesis of tricarboxylic acids and accordingly deserves further attention than it has received so far.
Abstract: Aerobacter aerogenes is able to utilize citric acid as sole source of carbon for growth in both aerobic and anaerobic conditions. From an analysis of fermentation liquors Deffner and Franke (1939) and Brewer and Werkman (1939) concluded that citric acid is decomposed anaerobically to oxalacetate and acetate as initial products. Manometric studies by the latter workers, using Aerobacter indologenes, showed that oxalacetic, pyruvic, and L-malic acids were fermented readily in addition to citric acid, and they also suggested that the \"citrate enzyme\" was adaptive rather than constitutive. Ajl and Werkman (1949) observed the effect of bisulfite and other inhibitors on the ability of citrate to replace the CO2 requirement of A. aerogenes and concluded that the aerobic decomposition of citric acid occurs by a different mechanism. Preparation of bacterial extracts which catalyze some of the reactions of the tricarboxylic acid cycle (Korkes et al., 1950; Stone and Wilson, 1952) has established a pathway for citrate oxidation by this mechanism. Krebs (1950) has drawn attention to the possibility that the dissimilation of citrate to oxalacetate and acetate may be a reversal of the synthesis of tricarboxylic acids and accordingly deserves further attention than it has received so far. For unaerated cultures of A. aerogenes relationships between bacterial crop and nutrient concentration are linear for glucose (Dagley et al., 1951) and citrate (Dagley et al., 1953) up to certain concentrations, beyond which further additions of carbon source produce no increase in crop in the presence of excess nitrogen source. Aeration of such cultures results in large increases in crop and further consumption of the source of carbon. Among the suggestions to account for the effect of aeration on glucose cultures is that of Fowler (1951) attributing fermentation to an unspecified adaptive enzyme, inactivated by oxygen. Since the effect of aeration on growth of cultures utilizing glucose and citrate is similar, it was of additional interest to study further the citric acid metabolism of A. aerogenes for which a definite adaptive enzyme has been postulated in anaerobic conditions.

34 citations

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TL;DR: other members of the cycle by vibrios grown at the expense of the aromatic acids, indicating either that the compound did not lie directly on the metabolic route or that its entry into the cell was prevented by permeability factors.
Abstract: other members of the cycle by vibrios grown at the expense of the aromatic acids, indicating either that the compound did not lie directly on the metabolic route or that its entry into the cell was prevented by permeability factors. That the latter view probably is correct is supported by preparation of extracts that oxidize 1 mole of citric acid with the uptake of 1 mole of 02 without initial lag. Cells were grown with aeration in 10 liters of defined medium (Dagley et al., 1952), and after harvesting 5 to 10 g of cell paste were crushed in the Hughes press previously cooled on solid CO, (Hughes, Brit. J. Exptl. Pathol., 32, 97, 1951), taken up in 20 ml of 0.02 M phosphate buffer (pH 7.0), and centrifuged at 7,000 G for 20 minutes to give a translucent extract. Rates of O2 uptake were determined in the Warburg respirometer: flasks contained 1 ml extract; 0.1 ml MgSO4, 0.02 M; 5 micromoles of citrate; and phosphate buffer to give a total volume of 3.0 ml. In table 1, rates of respiration for suspensions (ca 5 mg dry weight cells per flask) also are given and show that initiaRly the whole celLs oxidize citrate at only a small fraction of the rate of oxidation for the substances that served as carbon source for growth. A similar comparison for extracts is not possible since the latter, in all cases, did not oxidize the growth substrates. Adipic acid is included in table 1 since its behavior is typical for dibasic acids of chain length >4 C. Intact cells grown at the expense of these compounds give very low initial rates of oxidation of citrate; about 1 mole 02 is readily taken up per mole of citrate in the presence of extracts.

5 citations


Cited by
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TL;DR: Dl-mandelate elicits immediate synthesis at a steady rate of the first two enzymes of the pathway, but two enzymes which act below the level of benzoate are synthesized only after a considerable lag, and Succinate and asparagine do not significantly repress the synthesis of the enzymes responsible for mandelate oxidation.
Abstract: Hegeman, G. D. (University of California, Berkeley). Synthesis of the enzymes of the mandelate pathway by Pseudomonas putida. I. Synthesis of enzymes by the wild type. J. Bacteriol. 91:1140–1154. 1966.—The control of synthesis of the five enzymes responsible for the conversion of d(−)-mandelate to benzoate by Pseudomonas putida was investigated. The first three compounds occurring in the pathway, d(−)-mandelate, l(+)-mandelate, and benzoylformate, are equipotent inducers of all five enzymes. A nonmetabolizable inducer, phenoxyacetate, also induces synthesis of these enzymes; but, unlike the metabolizable inducer-substrates, it does not elicit synthesis of enzymes that mediate steps in the pathway beyond benzoate. Under conditions of semigratuity, dl-mandelate elicits immediate synthesis at a steady rate of the first two enzymes of the pathway, but two enzymes which act below the level of benzoate are synthesized only after a considerable lag. Succinate and asparagine do not significantly repress the synthesis of the enzymes responsible for mandelate oxidation.

396 citations

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13 Sep 1968-Science

253 citations

Book ChapterDOI

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170 citations

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TL;DR: Two strains of Pseudomonas were grown with phenol and used to prepare cell extracts that metabolized catechol with the transient formation of 2-hydroxymuconic semialdehyde and aldolase, which appeared to attack only one enantiomer of synthetic 4-hydroxy-2-oxovalerate.
Abstract: 1 Two strains of Pseudomonas were grown with phenol and used to prepare cell extracts that metabolized catechol with the transient formation of 2-hydroxymuconic semialdehyde 2 One of these preparations catalysed the conversion of 1mol of catechol into 1mol each of formate and 4-hydroxy-2-oxovalerate 3 A method for the determination of 4-hydroxy-2-oxovalerate is described, together with some properties of this compound and its 2,4-dinitrophenylhydrazone 4 Another partially purified cell extract converted 1mol of 4-hydroxy-2-oxovalerate, formed enzymically from catechol, into 1mol each of acetaldehyde and pyruvate This aldolase had a pH optimum of about 88, was stimulated by Mg(2+) ions and appeared to attack only one enantiomer of synthetic 4-hydroxy-2-oxovalerate

154 citations

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TL;DR: Several species of enterobacteria are able to utilize citrate as carbon and energy source during anaerobiosis, and enzymes specifically required for citrate fermentation are induced under anoxic conditions in the presence of citrate and Na+ ions.
Abstract: Several species of enterobacteria are able to utilize citrate as carbon and energy source. Under oxic conditions in the presence of a functional tricarboxylic acid cycle, growth on this compound solely depends on an appropriate transport system. During anaerobiosis, when 2-oxoglutarate dehydrogenase is repressed, some species such as Klebsiella pneumoniae and Salmonella typhimurium, but not Escherichia coli, are capable of growth on citrate by a Na+-dependent pathway forming acetate, formate, and CO2 as products. During the last decade, several novel features associated with this type of fermentation have been discovered in K. pneumoniae. The biotin protein oxaloacetate decarboxylase, one of the key enzymes of the pathway besides citrate lyase, is a Na+ pump. Recently it has been shown that the proton required for the decarboxylation of carboxybiotin is taken up from the side to which Na+ ions are pumped, and a membrane-embedded aspartate residue that is probably involved both in Na+ and in H+ transport was identified. The Na+ gradient established by oxaloacetate decarboxylase drives citrate uptake via CitS, a homodimeric carrier protein with a simultaneous-type reaction mechanism, and NADH formation by reversed electron transfer involving formate dehydrogenase, quinone, and a Na+-dependent NADH:quinone oxidoreductase. All enzymes specifically required for citrate fermentation are induced under anoxic conditions in the presence of citrate and Na+ ions. The corresponding genes form a cluster on the chromosome and are organized as two divergently transcribed operons. Their co-ordinate expression is dependent on a two-component system consisting of the sensor kinase CitA and the response regulator CitB. The citAB genes are part of the cluster and are positively autoregulated. In addition to CitA/CitB, the cAMP receptor protein (Crp) is involved in the regulation of the citrate fermentation enzymes, subjecting them to catabolite repression.

153 citations