Research

Post-translational modifications

After their translation (biosynthesis), proteins undergo various enzymatic and non-enzymatic, reversible and non-reversible changes at their site of origin and in their target organs and organelles. These so-called post-translational modifications (PTM) are numerous and affect practically all proteinogenic amino acids. The functions of a few post-translationally modified proteins (e.g. in histones) have long been known, well studied and understood. Examples include phosphorylation and glycosylation in signal transduction and enzyme activity. In contrast, the functions of a large number of post-translationally modified proteins are insufficiently studied and poorly understood. This is largely due to the fact that the number of proteins is astronomically high and their study requires the application of highly specialized instrumental analytical techniques coupled with appropriate high-performance computer-assisted software. Proteomics, a mass spectrometry-based technique, is becoming increasingly successful and satisfactory in accomplishing this task. Since proteins are made up of amino acids, unmodified amino acids and their modifications can be determined much more easily and cost-effectively using gas chromatography-mass spectrometry (GC-MS) with very high accuracy and precision. Low molecular weight substances, the so-called biomarkers, are released during regular proteolysis and can be measured in biological samples (blood, urine, saliva, tissue) from healthy and diseased individuals. The release of modified amino acids from post-translationally modified proteins is carried out chemically (6 M HCl, 110°C, 20 h). It is of interest whether modified proteins and the amino acids released from them have biological activities. The measurement of low-molecular and high-molecular PTM biomarkers allows a better understanding of the development and progression of diseases and can also contribute to effective therapeutic strategies.
In cooperation with national and international research groups, our working group is investigating the following PTMs: N-methylation of L-arginine and L-lysine, citrullination of L-arginine, glycation of L-arginine, L-lysine and L-cysteine, hydroxylation of lysine and proline, and hypusination of lysine. The latter only occurs in the eukaryotic translation factor (eIF5A), is enzymatic and strictly spermidine-dependent. Native and modified amino acids are derivatized with suitable chemical reactions (esterification, acylation) for GC-MS analysis. The focus of our experimental, clinical and clinical-pharmacological studies in adults and children/adolescents is the role of PTM in renal, cardiovascular and rheumatic diseases as well as in diabetes. We are also investigating the effect of exercise and diet on possible changes in PTM. Of current interest is whether possible health consequences of long-COVID have their origin in PTM.