Protein glycation in vivo: functional and structural effects on yeast enolase

Protein glycation is involved in structure and stability changes that impair protein functionality, which is associated with several human diseases, such as diabetes and amyloidotic neuropathies (Alzheimer's disease, Parkinson's disease and Andrade's syndrome). To understand the relationship of protein glycation with protein dysfunction, unfolding and beta-fibre formation, numerous studies have been carried Out ill vitro. All of these previous experiments were conducted in non-physiological or pseudo-physiological conditions that bear little to no resemblance to what may happen in a living cell. Ill vivo, glycation occurs in a crowded and organized environment, where proteins are exposed to a steady-state of glycation agents, namely methylglyoxal, whereas ill vitro, a bolus of a suitable glycation agent is added to diluted protein samples. Ill the present study, yeast was shown to be all ideal model to investigate glycation ill vivo since it shows different glycation phenotypes and presents specific protein glycation targets. A comparison between it? vivo glycated enolase and purified enolase glycated ill vitro revealed marked differences. All effects regarding structure and stability changes were enhanced when the protein was glycated ill vitro. The same applies to enzyme activity loss, dimer dissociation and unfolding. However, the major difference lies in the nature and location of specific advanced glycation end-products. Ill vivo, glycation appears to be a specific process, where the same residues are consistently modified in the same way, whereas ill vitro several residues are modified with different advanced glycation end-products.