The amino acid composition of the organic matrix and the neutral-soluble and acid-soluble components of embryonic bovine enamel

Abstract

Approximately 75-90% of the proteins of bovine embryonic enamel is soluble in cold neutral buffers of low ionic strength. The insoluble residue is readily dissolved in cold dilute acetic acid. The amino-acid compositions of the neutral-soluble fractions differed significantly from the acid-soluble fraction. The decalcified organic matrix of incisor enamel has smaller proline and histidine contents and a higher serine content than the organic matrix of premolar enamel. These differences which reflect the earlier development and maturation of the incisor teeth indicate that maturation of enamel is accompanied by a loss of protein components rich in proline and histidine and poor in serine. Small amounts of 3- and 4-hydroxyproline occur in all protein fractions. The 3-hydroxyproline4-hydroxyproline ratio in enamel is higher than that of either bovine dentinal or cemental collagen, suggesting that at least a portion of the hydroxyprolines are true constituents of the organic matrix of developing enamel.