title: Phosphorylation of chondroitin sulfate in proteoglycans from the swarm rat chondrosarcoma.
abstract: 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.
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002807:Chondroitin / Q000031:analogs & derivatives*; D002809:Chondroitin Sulfates / Q000378:metabolism*; D002813:Chondrosarcoma / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009844:Oligosaccharides / Q000302:isolation & purification; D010766:Phosphorylation; D011509:Proteoglycans / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
chemical_list: D009844:Oligosaccharides; D011509:Proteoglycans; D002807:Chondroitin; D002809:Chondroitin Sulfates