The composition of the organic matrix of bovine cementum

Abstract

The insoluble matrix of bovine cementum remaining after decalcification and extraction with a tris-NaCl buffer, had an amino acid composition which was generally characteristic of collagen but showed some differences from the comparable fraction of coronal cementum bone and dentine. An insoluble non-collagenous glycoprotein was a minor component. As in other calcified tissues, dehydrohydroxylysinohydroxynorleucine was the major reducible cross-link, although it occurred in a smaller amount than in dentine collagen. However, the latter contains less of the minor cross-link, dehydrohydroxylysinonorleucine, than was present in cementum collagen. A small quantity of material containing phosphorus was found in the non-diffusible fraction obtained after periodate degradation of the insoluble matrix, but a phosphoprotein of the type found in dentine was not detected after polyacrylamide gel electrophoresis. After papain digestion of the insoluble matrix, the neutral sugar compositions of the separated collagen and non-collagen glycopeptides were determined. The cementum collagen contained more hexose than skin or bone collagens, but less than cartilage collagens.