A computational investigation of the reactions of tyrosyl, tryptophanyl, and cysteinyl radicals with nitric oxide and molecular oxygen

PEDRON, FEDERICO N.; BARTESAGHI, SILVINA; ESTRIN, DARÍO A.; RADI, RAFAEL; ZEIDA, ARI

FREE RADICAL RESEARCH

TAYLOR & FRANCIS LTD

Año: 2019 vol. 53 p. 18 - 25

1071-5762

Proteins are main targets of oxidants in biological systems. This oxidation may occur in the protein backbone as well as in certain amino acid side chains, depending on the oxidant and amino acid intrinsic reactivity. Moreover, many enzymes are capable of generating stable amino acid radicals, such as tyrosyl, tryptophanyl and cysteinyl radicals. These species react very rapidly (many times as diffusion-controlled reactions) with relevant cellular open-shell species such as nitric oxide (·NO) or molecular oxygen (O 2 ). The exception to this apparent rule is tyrosyl radical, that reacts at diffusion rates with ·NO, but shows very slow reactivity towards O 2 (rate constant