Structural Analysis of Holothurian Fucosylated Chondroitin Sulfates: Degradation Versus Non-destructive Approach

Fucosylated chondroitin sulfates (FCS) are unique glycosaminoglycans isolated from the body walls of sea cucumbers (holothuria). These biopolymers are composed of a chondroitin core [→4)-β-d-GlcA-(1 → 3)-β-d-GalNAc-(1→] bearing fucosyl branches and the sulfate groups. Fucosyl substituents prevent enzymatic degradations of FCS by chondroitinases, which are effectively used in the structural analysis of vertebrate chondroitin sulfates, and hence, several non-enzymatic approaches to structural elucidation of FCS have been developed. They include combination of chemical modifications, specific degradation of polymeric chain and spectroscopic investigations of the products. In addition, there are examples of successful determination of the structure of non-modified FCS using NMR spectroscopic methods. NMR spectroscopy is especially effective in characterization of molecules with regular distribution of substituents along the polymeric chains. Otherwise combination of both chemical and spectroscopic methods is required for unambiguous elucidation of non-regular FCS structures. Structural variations of FCS studied up to now were shown to be species specific and include differences in type, amount and position of branches, as well as in degree and pattern of sulfation. These features of FCS can modify significantly the spectrum of their biological activities. In this mini-review the scopes and limitations of different approaches to FCS structure determination are concisely described and compared.