V. Sabareesh
Vellore Institute of Technology (VIT) University, India
Title: Arginine modification by 1,2-dicarbonyl compounds studied by liquid chromatography - electrospray ionization mass spectrometry (LC-ESI-MS)
Biography
Biography: V. Sabareesh
Abstract
1,2-dicarbonyl compounds are highly selective in covalently modifying sidechain guanidine group of arginine. Hence, these compounds find application for understanding the importance of arginine in enzymes, e.g. ATPase, kinase, etc. that recognize anionic substrates. Studies by radioactive 14C labeled phenylglyoxal (PG) or electrospray ionization mass spectrometry (ESI-MS) show that either 1 or 2 molecules of PG modify guanidine moiety of arginine in enzymes; whereas MS based investigations indicate addition of only one molecule of 1,2-cyclohexanedione (CHD) onto guanidine group of arginine in proteins/peptides. To attain clearer insights, herein we decided to probe amino acid L-arginine (L-Arg) modification by liquid chromatography (LC) - ESI-MS (LC-ESI-MS). Reactions were conducted using equimolar concentrations of reactants at room temperature (250C) in seven different mediums. In borate buffer, exclusively 1:1 adduct of L-Arg:PG (m/z 309) is observed. However, with CHD, L-Arg forms 1:1 adduct (m/z 287), 1:2 adduct (m/z 399) and respective water condensed products (m/z 269 & m/z 381) in borate. Interestingly, in water medium too, L-Arg is modified yielding condensed and uncondensed products of both 1:1 and 1:2 stoichiometries with PG as well as CHD. This is the first LC-ESI-MS study on L-Arg modification accomplished by phenylglyoxal and 1,2-cyclohexanedione. Additionally, observations from modification by 2,3-butanedione and LC-ESI-tandem MS (MS/MS) investigations on some model peptides containing one or two arginines shall be discussed. Furthermore, results obtained from the experiments conducted on a model protein, bovine pancreatic ribonuclease A will also be presented.