Confirmation of the site of nitrosation in tryptophan derivatives by α-chymotrypsin

N-Aroyl derivatives of aromatic hydrophobic L-amino-acid esters (1)-(7) are hydrolysed by a-chymotrypsin to the corresponding L-amino-acids (8)-(14). When the amidic nitrogen atom is incorporated into a heterocyclic ring, e.g. in the benzotriazinones (15a and b), substrate properties are lost. The N-nitroso-derivatives of N-acetyl-L-tryptophan methyl and ethyl esters are smoothly hydrolysed by a-chymotrypsin; their nitroso-groups are therefore attached to the indolic rather than the amidic nitrogen atom.