Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.6.4 (chondroitinase)
 2,039 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

13C nmr spectral parameters were measured for intact bovine nasal cartilage tissue, the purified proteoglycan aggregate, and chondroitin 4-sulfate. A comparison of integrated intensities obtained for four different samples of fresh tissue with an ethylene glycol standard indicated that at least 80% of the total glycosaminoglycan carbons in the tissue contributed to the spectrum. This result was confirmed by intensity measurements obtained at 56 degrees on fresh tissue and at 37 degrees after extensive papain digestion of fresh tissue. Spin lattice relaxation times and nuclear Overhauser enhancements were analyzed in terms of the following models of molecular motion: (a) single correlation time; (b) log X2 distribution of correlation times; and (c) anisotropic motion. The analysis indicates that the segmental motions of glycosaminoglycan chains are characterized by a broad distribution of correlation times centered at about 50 ns. Slow motion contributions to glycosaminoglycan line widths were reduced by dipolar decoupling (gammaH2/2pi = 65 kHz). Collagen intensity was observed in dipolar decoupled spectra, but not in scalar decoupled spectra of intact tissue, showing that the type II collagen in cartilage undergoes anisotropic motion like the type I collagen in tendon. Only glycosaminoglycan resonances were observed in spectra of a solution of proteoglycan aggregate before and after chondroitinase digestion. After subsequent digestion with papain, protein resonances were observed. These results suggest that the protein portions of the proteoglycan aggregate structure, in contrast with the glycosaminoglycan chains, have restricted backbone mobility and consequently a defined backbone structure.
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PMID:Investigation of molecular motion of proteoglycans in cartilage by 13C magnetic resonance. 14 Aug 75

13C NMR was used to study the molecular dynamics of the chick limb bud proteoglycan core protein. Because only about 10% of the proteoglycan is protein, [2-13C]glycine and [3-13C]serine were incorporated into the core protein of the chick limb bud proteoglycan monomer using a chondrocyte culture system. The purified labeled monomer was studied in solution (50 mg/ml, 0.05 M sodium acetate/0.05 M sodium phosphate, pH 7.4) at 37 degrees C. Spin-lattice relaxation times, line widths, and nuclear Overhauser enhancements were measured for the labeled carbons in the protein and for the natural abundance carbons in the glycosaminoglycan chains. Analyses of these data show that correlation times for backbone reorientation of protein and polysaccharide chains in the intact monomer are predominantly in the range of 0.5-5.0 ns. These correlation times are 10(2)-10(3) times smaller than the minimum correlation time calculated for a rigid monomer, indicating that the core protein and polysaccharide backbones are segmentally flexible. Signal intensity data show that at least 80% of the protein backbone is flexible but do not exclude the possibility that 20% of the protein backbone has ordered structure. We observe both broad and narrow signal components in the spectrum of the intact monomer, showing that backbone motion is heterogeneous. The broad signal component is not observed after the monomer is digested with chondroitinase. This result and the strong concentration dependence of the 13C line width observed in solutions of chondroitin 4-sulfate suggest an assignment of the broad signal component to residues near the protein-polysaccharide linkage region. The difference in NMR parameters observed for free and substituted serine carbons confirms that motion of the substituted serine side chain is restricted.
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PMID:13C nuclear magnetic resonance suggests a flexible proteoglycan core protein. 678 60