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W V HOWES

Publications and source records attributed to W V HOWES.

3 recordsLinked to original sources
PubMed1962

Isocitrate lyase and malate synthase in Pseudomonas indigofera. I. Suppression and stimulation during growth.

Howes, William V. (Washington State University, Pullman) and Bruce A. McFadden. Isocitrate lyase and malate synthase in Pseudomonas indigofera. I. Suppression and stimulation during growth. J. Bacteriol. 84:1216-1221. 1962.-Specific activities of isocitrate lyase and malate synthase from Pseudomonas indigofera were studied as a function of growth. Each activity maximized in the mid to late exponential phase. Effects upon levels of isocitrate lyase and malate synthase of each of several compounds supplied with ethanol to P. indigofera were next investigated. Compounds tested were glucose, glyoxylate, malate, and yeast extract. Each was added at various concentrations to ethanol. At higher concentrations, glucose, malate, and yeast extract suppressed both enzymatic activities. Malate synthase was more sensitive to suppression. Glyoxylate, at higher concentrations, suppressed isocitrate lyase but substantially stimulated malate synthase. There was no evidence for diauxic growth. Each substrate furnished with ethanol stimulated growth. The possibility that in vivo control of isocitrate lyase activity was partially exerted through feedback inhibition by succinate was examined. Succinate at 5.2 x 10(-3)m inhibited the enzyme in "soluble" preparations. Intracellular succinate concentrations did not vary significantly at each of three growth phases when exogenous succinate was supplied. Thus, regulation of isocitrate lyase activity through feedback inhibition by succinate seems unlikely.

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PubMed1962

Isocitrate lyase and malate synthase in Pseudomonas indigofera. II. Enzyme changes during the phase of adjustment and the early exponential phase.

Howes, William V. (Washington State University, Pullman) and Bruce A. McFadden. Isocitrate lyase and malate synthase in Pseudomonas indigofera. II. Enzyme changes during the phase of adjustment and the early exponential phase. J. Bacteriol.84:1222-1227. 1962.-The differential rates of synthesis (DRS) of malate synthase and isocitrate lyase were investigated at 30 C during the phase of adjustment (lag) and the early exponential phase in Pseudomonas indigofera. Cells grown on ethanol-acetate-yeast extract or succinate-yeast extract were added to a medium containing ethanol or succinate, and the DRS of each enzyme was followed. A reproducible decline in both enzymatic activities occurred after inoculation when a lag in growth was observed. To define the DRS occurring after this decline, a new parameter, epsilon, was defined and calculated for linear segments of a DRS plot. Certain variations of epsilon during DRS suggested that a balance between induction (or derepression) and repression controls, in part at least, malate synthase and isocitrate lyase levels. Effects of chloramphenicol upon enzyme synthesis after the period of expected decline were studied. No degradation or synthesis of malate synthase occurred in the presence of chloramphenicol, although, after degradation, slight synthesis of isocitrate lyase occurred. Acetate, butyrate, ethanol, glyoxylate, and isocitrate did not stimulate production of either enzyme in nongrowing cultures of high cell density. In fact, some degradation of each enzyme occurred.

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