Structural characterisation of chondroitin sulphate from Italian cheese Parmigiano-Reggiano

Chondroitin sulphate (CS) was purified for the first time from the Italian cheese Parmigiano-Reggiano and analysed to evaluate its structure and properties. Two main polysaccharides were identified as CS, ∼72%, and fast moving-heparin/heparan sulphate, ∼28%. Quantitative analyses yielded ∼1.5–3.0 μg of total GAGs per gram of Parmigiano-Reggiano (0.15–0.30%). By means of specific chondroitinases and HPLC separation of generated unsaturated disaccharides, CS was found to be composed of ∼9% of nonsulphated disaccharide, ∼26% of disaccharide monosulphated in 6 of the GalNAc, ∼65% of disaccharide monosulphated in 4 of the GalNAc, with a charge density of ∼0.91 and a 4/6-sulphated ratio of 2.45. The ratio of 4/6 sulphated residues was confirmed by 13C NMR experiments. Susceptibility to cleavage catalysed by chondroitinase B confirmed that the purified Parmigiano-Reggiano CS contains mainly GlcA (∼94%) as uronic acid. PAGE analysis showed a CS having a molecular mass with an average value of 15400.