A Review of Methionine and Cysteine: Their Roles as Sinks for Reactive Oxygen and Nitrogen Species, Including Bioinformatic Analysis of Their Percent Compositions in Metabolic Proteins.

This review focuses on the roles of the two primary sulfur-containing amino acids, cysteine and methionine, in regulating reactive oxygen/nitrogen species (RONS). RONS are highly reactive oxygen/nitrogen-containing free radicals and compounds. Endogenous and exogenous antioxidants, including sulfur-containing amino acids, protect cells against the harmful effects of RONS on cellular macromolecules. This study thoroughly reviews the mechanisms by which these two sulfur-containing amino acids neutralize RONS. Additionally, a bioinformatic analysis of the percentage compositions of cysteine and methionine in metabolic proteins of humans and 12 closely related species was conducted using a "Biopython" script to assess their potential role as sinks for RONS, maintaining the structure and function of metabolic proteins. A total of 119 proteins from various metabolic pathways, including glycolysis, pyruvate to acetyl CoA conversion, tricarboxylic acid cycle, oxidative phosphorylation, pentose phosphate pathway, gluconeogenesis, glycogen metabolism, fatty acid metabolism, amino acid catabolism, nucleotide biosynthesis, and ROS scavengers were included in the bioinformatics analysis. This review shows that methionine and cysteine play crucial roles in neutralizing RONS. The bioinformatic analysis revealed that the percentage compositions of methionine and cysteine are higher in key redox enzymes like dehydrogenases, enzymes involved in oxidative phosphorylation, and those participating in the committed steps of metabolic pathways.

Supplementary information: The online version contains supplementary material available at 10.1007/s12291-024-01284-y.