Studies on Kinetics of Reaction Between Peroxynitrite and Tryptophan

Peroxynitrite (ONOO-) is a potent cytotoxin, and it can damage tryptophan, tyrosine and other biomolecules. The kinetics of tryptophan damaged by peroxynitrite was studied by stopped-flow spectrophotometer at 25degC. When peroxynitrite is present in excess, there are many products formed including nitrotryptophan, hydroxytryptohan, N-formylkinurenine or dihydroxytryptophan, oxindole, and hydropyrroloindole. The kinetics of tryptophan loss can represent the kinetics of peroxynitrite damaging tryptophan as a whole. The kinetics of this reaction was studied by monitoring the decrease of fluorescence of tryptophan, and the apparrent second order rate, 2.85 x 10⁴ M^middot1 s^middot1, and the apparent activation energy, 39.4 kJ-mol^middot1 are derived.