ABSTRACT
The proteome consists of the expressed proteins in a cell, tissue, or organism. Whereas one gene in principle encodes for one protein, the expressed protein may occur as a population of heterogenous species in various modification states, involving among others phosphorylation and glycosylation. In fact, more than 200 modification types have been recorded, while new ones are being discovered. These modified forms of one protein, often indicated as post-translation modifications (PTM), may be present at different locations in the cell and in widely different concentrations. PTM are known to determine targeting, structure, function, and turnover of proteins. They play an important role in the regulatory actions with respect to the biological activity of the protein. PTM result from a variety of mechanisms, involving both enzymatic and nonenzymatic reactions in the cell. They may also be due to interactions between proteins and xenobiotics. The analysis of a wide variety of protein adducts was reviewed [1].
