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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.
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PMID:Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum. 673 86

Utilization of the tricarboxylic acid (TCA) cycle intermediates, L-malic acid and succinic acid, by the yeast Pachysolen tannophilus is repressed in the presence of glucose. Strains of P. tannophilus containing mutations in two hexokinases and a glucokinase were characterized for growth on glucose plus L-malic acid or succinic acid. Increased specific utilization rates of malic acid and succinic acid in the presence of glucose were observed in mutants containing a lesion in hexokinase A, an enzyme associated with catabolite repression. Such derepressed mutants may have application in winemaking in which utilization of a major grape acid, L-malic acid, is often desirable for acidity reduction.
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PMID:Derepressed utilization of L-malic acid and succinic acid by mutants of Pachysolen tannophilus. 924 68