Global chemical modifications comparison of human plasma proteomes from two different age groups

The chemical modification of proteins refers to the covalent group reaction involved in their amino acid residues or chain ends which, in turn, change the molecular structure and function of the proteins. There are many types of molecular modifications in the human plasma proteome, such as phosphorylation, methylation, and acetylation. In this study, two groups of human plasma proteome at different age groups (old and young) were used to perform a comparison of global chemical modifications, as determined by tandem mass spectrometry (MS/MS) combined with non-limiting modification identification algorithms. The sulfhydryl in the cysteine A total of 4 molecular modifications were found to have significant differences: the succinylation and phosphorylation modification of cysteine (Cys, C) and the modification of lysine (Lys, K) with threonine (Thr, T) were significantly higher in the old group than in the young group, while the carbamylation of lysine was lower in the young group. Cysteine residue is an important group for forming disulphide bonds and maintaining the structure of the protein. Differential cysteine-related sulfydryl modifications may cause structural and functional changes. Lysine is a basic amino acid, and the modification of its amino group will change the charge state of the protein, which may affect the structure and function of the protein. In summary, four types of protein chemical modifications and substitutes were found to be significantly different in the plasma proteome in different age groups and their probabilities of random generation are lower by passing random grouping test. We speculate that there is an increase in certain modified proteins in the blood of the old people which, in turn, changes the function of those proteins. This change may be one of the reasons why the old people are more likely than the young people to be at risk for age-related diseases, such as metabolic diseases, cerebral and cardiovascular diseases, and cancer.