Effect of tryptophan and its metabolites on gluconeogenesis in mammalian tissues.
In parenchymal cells from starved mice L-tryptophan is a potent inhibitor of gluconeogenesis from substrates giving rise to oxaloacetate. Quinolinate yields a different pattern of inhibition and is generally much less effective. Tryptamine, indole 3-acetaldehyde and indole 3-acetate are equally as effective as tryptophan. Tryptamine inhibition alone may be overcome by pargyline; serotonin does not prevent the inhibition due to tryptophan. In kidney slices from starved rats, however, tryptophan has no effect on gluconeogenesis. Indole 3-acetate is also relatively ineffective, but quinolinate is signficiantly more potent than in liver; at 0.1mM, glucose production from lactate is 50% inhibited. Quinolinate is less effective with citric acid cycle substrates; the pattern of inhibition is consistent with a direct action on phosphoenolpyruvate carboxykinase. There is no evidence that glutamate dehydrogenase is simultaneously inhibited.
D000818:Animals; D005943:Gluconeogenesis / Q000187:drug effects*; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D011725:Pyridines / Q000494:pharmacology*; D011805:Quinolinic Acids / Q000494:pharmacology*; D051381:Rats; D014364:Tryptophan / Q000378:metabolism / Q000494:pharmacology*
D011725:Pyridines; D011805:Quinolinic Acids; D014364:Tryptophan