Phosphorylation of chondroitin sulfate in proteoglycans from the swarm rat chondrosarcoma

• Published in: The Journal of biological chemistry 1984-02, Vol.259 (3), p.1720-1726
• Main Authors: Oegema, T R, Kraft, E L, Jourdian, G W, Van Valen, T R
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Carbohydrate Conformation; Carbohydrate Sequence; Chondroitin - analogs & derivatives; Chondroitin Sulfates - metabolism; Chondrosarcoma - metabolism; Diseases of the osteoarticular system; Kinetics; Magnetic Resonance Spectroscopy; Medical sciences; Oligosaccharides - isolation & purification; Phosphorylation; Proteoglycans - isolation & purification; Proteoglycans - metabolism; Rats; Tumors of striated muscle and skeleton
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)43466-1

Proteoglycans isolated from the Swarm rat chondrosarcoma were shown to contain 35 mol of phosphate/mol of proteoglycan. While 20% of this phosphate was released by digestion with dilute alkali in the presence of sodium borohydride and is presumably of the phosphoserine/phosphothreonine type, 78% of the phosphate copurified with the peptide-free chondroitin sulfate chains. When chondroitin sulfate chains purified by ethanol precipitation or Sephacryl S200 column chromatography were digested with chondroitinase AC and the digests chromatographed on Bio-Gel P-4, the phosphate co-migrated with a carbohydrate fragment that contained 2 glucuronic acid (one as delta 4,5-unsaturated sugar), 1-galactosamine, 2-galactose, and 1-phosphate residue/xylitol. A second fragment of similar composition but lacking phosphate was also recovered in a ratio of about 3 to 1 relative to the phosphorylated fragment. The phosphate in the chondroitin sulfate linkage region fragment had the alkaline phosphatase sensitivity as well as 31P NMR spectra of a monophosphate esterified to a secondary sugar alcohol. The phosphate was localized on the C-2 of the chain initiating xylose since these residues as xylitol showed a delayed release during acid hydrolysis and the xylitol was recovered intact after periodate oxidation. In the chondrosarcoma, 2-phosphoxylose appears to be a normal synthetic product since [32P]phosphate was readily incorporated into the proteoglycan and the incorporated isotope had similar biochemical properties as the unlabeled phosphate.