Navegando por Autor "Dias, Maria da Conceição Loureiro"

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Glycerol utilization in Fusarium oxysporum var lini : regulation of transport and metabolism.
(1991) Castro, Ieso de Miranda; Dias, Maria da Conceição Loureiro
Glycerol was transported in the fungus Fusarium oxysporum var. lini by a facilitated diffusion transport system with a half-saturation constant, Ks, of 0.5 mM and a maximum velocity, Vmax, of 0.9 mmol (g dry wt)-l h-l at pH 5 and 25OC. 1,2-Propanediol was a competitive inhibitor of glycerol transport, but the cells did not actively accumulate 1,2-propanediol. The transport system was partially constitutive. In cells grown in the presence of glucose, glycerol was not transported, indicating that the synthesis of the system was under glucose repression. Glycerol base and NADP+-dependent glycerol dehydrogenase activities were present under all physiological conditions tested. A flavin-dependent glycerol phosphate dehydrogenase was induced only when glycerol was the sole energy source in the medium. This enzyme, together with the transport system, constitute the regulated steps in the glycerol metabolic pathway.
Regulation of sugar transport systems in Fusarium oxysporum var. lini.
(1990) Brandão, Rogélio Lopes; Dias, Maria da Conceição Loureiro
Fusarium oxysporum var. Iini (ATCC 10960) formed a facilitated diffusion system for glucose (Ks, about 10 mM) when grown under repressed conditions. Under conditions of derepression, the same system was present together with a high-affinity (K5, about 40 ,iM) active system. The maximum velocity of the latter was about 5% of that of the facilitated diffusion system. The high-affinity system was under the control of glucose repression and glucose inactivation. When lactose was the only carbon source in the medium, a facilitated diffusion system for lactose was found (Ks, about 30 mM).
Utilization of lactic acid by Fusarium oxysporum var. lini : regulation of transport and metabolism.
(1994) Castro, Ieso de Miranda; Dias, Maria da Conceição Loureiro
Lactic acid was transported in Fusarium oxysporum var. lini ATCC 10960 by a saturable transport system that had a half-saturation constant of 56.6 7.5 FLM and a maximum velocity of 0.61 0.10 mmol h-1 g-1 (dry weight) at 26°C and pH 5.0. This transport system was inducible and was not expressed in the presence of a repressing substrate. Evidence is presented that the anionic form lactate- was taken up by the cells. Propionic, acetic, pyruvic, and bromoacetic acids but not succinic acid competitively inhibited the transport of lactic acid. Bromoacetic acid, which was not metabolized, was taken up to a steady-state level when intracellular and extracellular concentrations were identical, indicating that the transport system was not accumulative. The enzymatic activity that was physiologically more relevant in the metabolism of lactic acid was lactate: ferricytochrome c oxidase. This enzyme did not exhibit stereospecifity and was induced by lactic acid.