PROTEINS IN EMBRYONIC BOVINE ENAMEL

Abstract

The fractionation and the amino acid composition of the organic matrix of embryonic bovine enamel was studied. EDTA- and water-soluble fraction dissolved in phosphate buffer showed a temperature-dependent properties; at low temperatures it formed a clear solution, but at room temperature heavy precipitations occurred. This phenomenon was reversible. EDTA- and water-soluble fraction prepared in mild conditions was first chromatographed on Sephadex G-25 column. Four fractions were obtained. The main fraction comprised nearly half of the material and its molecular weight was found by gel filtration to be greater than 3,500. The temperature-dependent phenomenon above stated was observed only in the main fraction. The result of the fractionation with Sephadex G-100 revealed that a portion of the main fraction had molecular weight greater than 100,000. The results of the amino acid analysis showed that the EDTA- and water-soluble fraction was a high proline component. On the other hand, the EDTA insoluble fraction was a high proline-glutamic acid-histidine component. The EDTA-insoluble fraction was extracted with organic solvents and water. About 73% was solubilized, and the amino acid composition of the extracted residue relatively changed from the mother fraction; the residual protein contained only small amount of histidine. These results were discussed with reference to enamel maturation.