The proteoglycan bikunin has a defined sequence

Proteoglycans are complex glycoconjugates that regulate critical biological pathways in all higher organisms. Bikunin, the simplest proteoglycan having a single glycosaminoglycan chain, is a serine protease inhibitor used to treat acute pancreatitis. Unlike the template driven synthesis of nucleic acids and proteins, Golgi synthesized glycosaminoglycans are not believed to have predictable or deterministic sequence. Bikunin peptidoglycosaminoglycans were prepared and fractionated to obtain a collection of size similar and charge similar chains. Fourier transform mass spectral analysis identified a small number of parent molecular-ions corresponding to mono-compositional peptidoglycosaminoglycans. Fragmentation using collision induced dissociation surprisingly afforded a single sequence for each mono-compositional parent-ion, unequivocally demonstrating the presence of a defined sequence. The common biosynthetic pathway for all proteoglycans suggests that even more structurally complex proteoglycans, such as heparan sulfate, may have defined sequences, requiring a readjustment of our understanding of information storage in complex glycans.