Amino-terminal location of pyridinoline in dentin collagen

Abstract

Cross-linking is believed to be one of the major factors that characterize the calcifiability of dentin and bone collagens. Dehydro-dihydroxylysinonorleucine and pyridinoline which constitute the principal cross-links of dentin collagen have so far been located only in the carboxy terminal telopeptide of the molecules [α1(I)-chain 87 × α1(I)-chain 16^c]. This situation suggested that the amino terminal telopeptide portion might be “open” without intermolecular cross-linking in hard tissue collagen fibrils. However, the present study provided evidence that pyridinoline is also located in amino-terminal telopeptides (α1-chain 9^N or α2-chain 5^N) and al-chain 930. Bovine dentin collagen was digested with trypsin followed by heating at 60°C before and after the digestion. This method gave complete trypsin peptides of dentin collagen. Fluorescent pyridinoline peptides with a smaller molecular size were isolated by Sephadex G-50 superfine, DEAE-cellulose and reverse-phase HPLC. Automatic Edman analysis of several isolated peptides revealed the five-residue sequence, Gly-Ile-X-Gly-His-Arg, the only assignment of which was al-chain 928–933. The above evidence together with the amino acid compositions of the peptides led to the conclusion that pyridinoline is located not only in the carboxy-terminal but also in the amino-terminal telopeptide in dentin collagen.

Key Words:

• pyridinoline
• collagen
• cross-links
• calcification