Tryptophan is glucogenic & ketogenic by producing -
Ans. is 'a* i.e^ Acetyl CoA & alanineo Tryptophan is metabolized to aeetyl-CoA which is ketogenic and also produces alanine which enters into gluconeogenesisMetabolism of tryptophano Tryptophan is an essential amino acidr, containing indol ring0. Tryptophan is oxidized to produce alanine (which is glucogenic) and acetyl-CoA (which is ketogenic). Therefore, tryptophan is both glucogenic and ketogenic. Tryptophan is precursor for thebiosvnthess of niacin0 (a vitaminr,), serotonin (a neurotransmitter) and melatoninr (a hormone).o Tryptophan metabolism occurs by two pathways: (i) kinurenine pathway0and (ii) serotonine pathway.1) Kvnurenine pathway:- Tryptophan is oxidized to kynurenine, which is then converted to either niacin (nicotinic acid) or acetyl-CoA. In the reaction alanine is also produced.o Deficiency of tryptophan can cause deficiency of niacin (if also deficient in diet). This can leads to Pallegra: dermatitis, diarrhea and dementia.o For every 60 mg of tryptophan, 1 mg. equivalent of niacin can be generatedro In vitamin B6 deficiency the metabolism is shuted to xanthurenic acid. Therefore, xantheurenic acid excretion is increased in urine.2) Serotonin pathway:- Tryptophan is first oxidized to serotonine which is further converted to melatonin.o Serotonin secretion is increased in carcinoid syndrome which causes flushing0, Vasoconstrictionr, diarrhear and bronchospasm (respiratory distress).
Acetyl Co A & alanine
Acetoacetate & fumarate
Acetoacetate & arginine
Arginine & alanine
Amino Acids Basics