[Isolation and characterization of proteoglycan in bovine periodontal ligament]

Proteoglycan, one of the major non-collagenous protein in the connective tissue, is bound with fibronectin and other cell adhesion proteins, and has a role in the formation of the tissue and the organ. Although the glycosaminoglycan components in various tissue have been widely investigated, the molecular structure of periodontal ligament proteoglycan (PDL-PG) was rarely reported. In present study, proteoglycans of bovine periodontal ligament were purified by chromatography from material adsorbed by DEAE-Sephacel from a guanidium HCl extract. The sequential chromatographic steps consisted of ion-exchange chromatography on DEAE-Sephacel in 4M urea and gel filtration on Sepharose CL-4B in 4M guanidium HCl. The preparation contained a relatively small proteoglycan (Mr = 132,000 dalton) and a free glycosaminoglycan chain (Mr = 88,000 dalton). A Mr = 58,000 dalton core protein was shown by gradient SDS gel electrophoresis after chondroitinase ABC or chondroitinase AC II treatment. The glycosaminoglycan chains after chondroitinase AC II hydrolysis were seen on gel as polydispersed, broad alcian blue staining material (Mr = 20,000-60,000 dalton) while chains were totally hydrolyzed by chondroitinase ABC. These indicate a chondroitin sulfate/dermatan sulate (CS/DS) hybrid glycosaminoglycan chain. Papain digestion of the proteoglycan resulted in a single glycosaminoglycan chain after SDS gel electrophoresis with no protein band. These results suggest that the PDL-PG is slightly larger than that of bone and contains a single chondroitin sulphate/dermatan sulphate chain attached to a 58 K core protein. Antisera raised against PDL-PGs cross-reacted with PDL-PGs but not with other PDL proteins or bone PGs. It has been shown that during biosynthesis of dematan sulfate, L-iduronic acid is formed by epimerization of D-glucuronic acid, and sulfation. The degree of epimerization and sulfation may be related to the function of PDL in buffering the mechanical force applied to the tooth.