N- tryptophan

Study of the interrelationship between insulinase, diabetes mellitus, and tryptophan (M9) revealed that n-tryptophan, administered either subcutaneously or by stomach tube in the amount 1-lmM/kg, produces a statistically highly significant hypoglycemia in the rat, whereas D-tryptophan and 16 other amino acids were ineffective when given by mouth in similar doses. In contrast to the effect produced in normal rats, there is no hypoglycemic response in severely diabetic alloxanized rats given L-tryptophan. 

Sano, K., Yokozeki, K., Eguchi, C., Kawaga, T., Noda, I. Mitsugi, K. Enzymatic production of N-tryptophan from L- and DL-5-indolylmethylhydantoin by newly isolated bacterium. Agric. Biol. Chem., 41 (1977) 819-825. 

L-Tryptophan is the only substance converted to kynurenine by the liver enzyme system. Such closely related compounds as n-tryptophan and acetyl-DL-tryptophan are not attacked. The reaction proceeds with the uptake of 1 molecule of O2 and causes the liberation of 1 mole of formic acid and 1 of kynurenine but no CO2. 

Incorporation of 2- C,l- N-tryptophan (29c) and examination of the NMR spectrum of the derived (1) has revealed the direction of p-carboline cleavage (42, 44). The presence and location of the label in (1) was determined from its spin-coupling (Jcn= 14.7 Hz) to the enriching at C-5, demonstrating that it was the original Nb-C7a bond of tryptophan which had been broken. Such a cleavage reaction of an indole or a P-carboline, either chemically or biochemically, is unprecedented. 

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