Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Queuine, 7-(( (4,5-cis-dihydroxy-2-cyclopenten-1-yl)-amino]-methyl)-7-deazagu ani ne is synthesized de novo only in eubacteria and is preseent in place of guanine 34 in specific tRNAs containing anticodones GUN where N is one of the four canonical nucleotides. The biosynthetic pathway starting with GTP shares common steps with that of pteridines and riboflavin, and involves iron ions and a 'vitamin B12' coenzyme. Lower and higher eukaryotes are supplied with queuine by nutrition or the intestinal flora. The modification of tRNA with queuine is tissue specific and depends on the metabolic state of cells and tissues. Starvation for queuine and/or Q-deficiency in tRNA causes a few specific changes in the pattern of protein synthesis involving lactate dehydrogenases and cytochromes.
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PMID:The nutrient factor queuine: biosynthesis, occurrence in transfer RNA and function. 307 30

Higher eukaryotes contain tRNA transglycosylases that incorporate the guanine derivative queuine from the nutritional environment into specific tRNAs by exchange with guanine at position 34. Alterations in the queuosine content of specific tRNAs are suggested to be involved in regulatory mechanisms of major routes of metabolism during differentiation. Dictyostelium discoideum has been applied as a model to investigate the function of queuine or queuine-containing tRNAs. Axenic strains are supplied with queuine by peptone, but they grow equally well in a defined queuine-free medium. Queuine-lacking amoebae, starved in suspension culture for 24 h, lose their ability to differentiate into stalk cells and spores, whereas amoebae sufficiently supplied with queuine will overcome this metabolic stress and undergo further development when plated on agar. The results presented here show that D(-)-lactate occurs in the slime mould in millimolar amounts and that its level is remarkably decreased in queuine-lacking cells after 24 h of starvation in suspension culture. On isoelectric-focusing polyacrylamide gels, nine different forms of NAD-dependent D(-)-lactate dehydrogenase can be separated from extracts of vegetative cells, and six forms from extracts of the starved cells. Under queuine limitation, one form is missing in the starved cells. Low amounts of L(+)-lactate are usually found in vegetative amoebae but significantly less in queuine-lacking cells. Five forms of NAD-dependent L(+)-lactate dehydrogenase are detectable in extracts from vegetative, queuine-treated cells, and slight alterations occur in queuine-deficient amoebae. In the starved cells only one form of L(+)-lactate dehydrogenase is found, irrespective of the supply of queuine to the cells. A cytochrome of type b with an absorption maximum at 559 nm accumulates during starvation only in queuine-lacking cells; it might be a component of an NAD-independent lactic acid oxidoreductase as is cytochrome b 557 in yeast and be responsible for the reduced level of lactate in cells lacking queuine in tRNA.
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PMID:Specific changes in lactate levels, lactate dehydrogenase patterns and cytochrome b559 in Dictyostelium discoideum caused by queuine. 669 26