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首页> 外文期刊>Archives of microbiology >Net efflux of citrate in Penicillium simplicissimum is mediated by a transport protein
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Net efflux of citrate in Penicillium simplicissimum is mediated by a transport protein

机译：柠檬酸在简单青霉中的净流出是由转运蛋白介导的

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Penicillium simplicissimum excreted citrate, isocitrate, and succinate when grown in a strongly buffer ed medium [1 M Mes (pH 6) or 1 M Hepes (pH 7.3)]. Growth in a weakly buffered medium did not lead to citrate excretion despite a similar intracellular citrate concentration. When nongrowing, citrate-excreting hyphae were aerated in a glucose solution, the following steady-state intracellular concentrations of organic acids were measured: succinate (25 mM); citrate, isocitrate, malate. and fumarate (all less than 5 mM). After 2 h of incubation, the extracellular concentrations of these acids were [mu mol (g dry wt.)(-1)]: isocitrate [100], citrate [60], succinate [30], and malate, fumarate, and a-ketoglutarate [<5]. The excretion of citrate was due neither to an unspecific change in the permeability of the plasma membrane nor to simple diffusion of undissociated citric acid. The involvement of a transport protein in citrate excretion was indicated because N-ethylmaleimide and sodium azide inhibited citrate excretion strongly despite an unchanged outward-directed citrate gradient. Arguments are given why efflux via a citrate uptake carrier is not considered probable. These results indicate that citrate is excreted by P. simplicissimum via a transport protein that probably specifically mediates the efflux of citrate. [References: 38]
机译：当在强烈缓冲的培养基[1 M Mes（pH 6）或1 M Hepes（pH 7.3）]中生长时，简单青霉会分泌柠檬酸，异柠檬酸和琥珀酸。尽管细胞内柠檬酸盐浓度相似，在弱缓冲培养基中的生长也不会导致柠檬酸盐排泄。在葡萄糖溶液中通气时，不分泌柠檬酸盐的菌丝通气，测量以下稳态的细胞内有机酸浓度：琥珀酸盐（25 mM）;柠檬酸盐，异柠檬酸盐，苹果酸。和富马酸盐（均小于5 mM）。孵育2小时后，这些酸的细胞外浓度为[μmol（g干重）（-1）]：异柠檬酸盐[100]，柠檬酸盐[60]，琥珀酸盐[30]和苹果酸，富马酸盐和a -酮戊二酸酯[<5]。柠檬酸盐的排泄既不是由于质膜渗透性的非特异性变化，也不是由于未解离的柠檬酸的简单扩散。指示转运蛋白参与柠檬酸盐的排泄，因为尽管未改变向外的柠檬酸盐梯度，但N-乙基马来酰亚胺和叠氮化钠强烈抑制柠檬酸盐的排泄。给出了为什么不认为经由柠檬酸盐摄取载体的外排是可能的。这些结果表明，简单的P. simplicissimum通过可能特异地介导柠檬酸流出的转运蛋白将柠檬酸盐排泄。 [参考：38]

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