Molecular Evolution of Glycoproteins

抄録

Glycopeptides have been systematically classified based on the carbohydrate-peptide linkages and on the structure of carbohydrate units, and the hypotheses have been proposed regarding the evolution of these glycopeptides. Of seven types of carbohydrate-peptide linkages so far established, only glucosaminylasparagine linkage evolved in the proto-eukaryote, common ancestor of all eukaryotes, whereas the remaining six types of linkages, which are all 0-glycosidic bonds to hydroxyamino acids, evolved when or after the protoeukaryotes diverged into three kingdoms, i.e., fungi, plants, and animals. This kingdom specificity of glycoproteins reflects the fact that eukaryotic kingdoms differ mainly in the intercellular matrix, the principal components of which are glycoproteins, rather than in the intracellular substances. It is suggested (i) that glycoproteins arose mainly concomitant with multicellular organisms, (ii) that the inventions of certain glycoproteins were the decisive events in evolutionary diversification, and (iii) that glycoproteins were essential for the development of tissues and organs, but not essential for the primitive life. To date no definitive proof has been provided for the presence of glycoproteins in prokaryotes.