Chemistry Colloquium | Non-Enzymatic Modifications in Mammals and Milk Products, Sept. 20

Ohio University’s Chemistry and Biochemistry Colloquium Series presents Dr. Ralf Hoffmann on “Non-Enzymatic Modifications in Mammals and Milk Products” on Tuesday, Sept. 20, at 4:10 p.m. in Clippinger Laboratories, Room 194.

Dr. Ralf Hoffmann

Hoffmann is Professor in the Department of Pharmaceutical Analysis at University of Leipzig, Germany.

Abstract:  Proteins are continuously modified in cells by enzymes (e.g. phosphorylation, glycosylation, methylation, acetylation or hydroxylation), which has attracted much biochemical and medical interest. However, reactive compounds can also modify functional groups in proteins. These non-enzymatic modifications are continuously produced in organisms including humans and also during food storage or cooking. These reactions affect proteins, peptides, lipids, DNA, and other biomolecules at different degrees. The products are typically considered harmful and are thus often studied in the context of diseases and aging, although the molecular mechanisms have not been revealed in much detail. We could establish analytical techniques for common classes of non-enzymatic modifications:

• Oxidation affects mostly cysteine, methionine, and tryptophan residues, but also all other canonical amino acids.
• Some oxidation products contain ‘reactive carbonyls’ (i.e. aldehydes or ketones) that can react with other residues within the same protein or irreversibly cross-link proteins.
• Aldoses and ketoses can modify lysine residues by a process called non-enzymatic glycosylation (or glycation), for example in diabetes patients, yielding Amadori- and Heyns- products, respectively.
• Oxidative degradation of the sugar moiety of glycated residues can yield numerous ‘advanced glycation endproducts’ (AGEs), which can also be formed by other non-enzymatic pathways.

The established techniques allowed us to study these protein modifications in human plasma samples to identify possible biomarkers for early diagnosis of type 2 diabetes and to judge the influence of industrial processing and consumer behavior on their contents in different milk products.