pH‐Dependent Nitrotyrosine Formation in Ribonuclease A is Enhanced in the Presence of Polyethylene Glycol (PEG)

Abstract

Protein nitration can occur as ar esult of peroxynitrite-mediated oxidative stress. Excess production of peroxynitrite (PN) within the cellular mediumc an cause oxidative damage to biomolecules.T he in vitro nitration of Ribonuclease A( RNase A) resultsi nn itrotyrosine (NT) formation with as trong dependence on the pH of the medium. In order to mimic the cellular environment in this study,P Nmediated RNase An itration has been carried out in ac rowd-ed medium. The degree of nitration is higher at pH 7.4 (physiological pH) compared to pH 6.0 (tumorc ell pH). The extent of nitration increases significantly when PN is added to RNase Ai nt he presence of crowding agentsP EG 400 and PEG 6000. PEG has been found to stabilize PN overaprolonged period,t hereby increasing the degree of nitration. NT formation in RNase Aa lso results in as ignificant loss in enzymatic activity.Scheme1.Generation of peroxynitrite and subsequent formation of nitrating species.

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“…Various literature has shown how peroxynitrite (ONOO − ) plays an important role in the biological action of cold plasma [ 26 , 27 , 28 ]. With a decrease in the pH of a solution treated with cold plasma from 7.4 to 6.0, its interaction with a tyrosine solution significantly reduces the formation of nitrotyrosine, a product of the interaction of tyrosine with ONOO − derivatives [ 27 ]. ONOO − in a solution treated with cold plasma is much better preserved at alkaline pH than at neutral or acidic pH [ 26 ].…”