The complexity of human life arises from some twenty thousand genes, and results due to alternative splicing mechanism in approx. 100000 proteins. By posttranslational modifications these proteins are converted into an array of some 1.5 million different functional entities. Interestingly, this conversion can either be enzymatically controlled and regulated, or may have an apparently random aspect due to non-enzymatic reactions. Proteins undergo a wide array of non-enzymatic post-translational modifications. Such modifications of proteins are often determined by their environments, their structural features and by a number of protecting structures, and also by free radicals generated in their vicinity. Non-enzymatic protein modifications are, therefore, not random, but occur in a non-regulated manner and depend largely on the protein and its environment.