Abstract
Bovine dental enamel matrix is partially soluble in certain organic solvents. On the assumption that this behavior was due to the presence of lipid, the neutral lipids of enamel were examined. Prior to demineralisation of the tissue it was possible to remove 44% of its total neutral lipid complement. Of the lipids removed, cholesterol esters, triglycerides and free fatty acids were predominant. Following demineralisation of the enamel, the residual lipids were liberated. The profile of lipids in this extract resembled the first. However, the total quantity of enamel lipid was insufficient to explain lipophilia on the basis of lipoprotein formation. Subsequently, the proteins of this tissue were examined. Gel exclusion chromatography revealed the presence of protein aggregates, possibly hydrophobically stabilised. On electrophoresis, differences between soluble and insoluble protein fractions were noted. Amino-acid analyses of these two protein fractions indicated a marked difference in their proline content. It was concluded that this non-polar amino acid was at least partially responsible for the unusual solubility properties of enamel matrix.
Résumé
La matrice d'émail de boeuf est partiellement solubilisé dans certains solvants organiques. En supposant que ce comportement soit lié à la présence de lipides, les lipides neutres de l'émail ont été étudiés. Avant déminéralisation, il est possible d'extraire 44% du complément des lipides neutres totaux. Parmi les lipides extraits, les esters du cholestérol, les triglycérides et les acides gras libres sont prédominants. Après déminéralisation de l'émail, des lipides résiduels sont libérés. La distribution lipidique de cet extrait est analogue au premier. Cependant, la quantité totale de lipide de l'émail n'est pas suffisante pour rendre compte de la lipophilie en fonction de la formation lipoprotéique. Les protéines de ce tissu ont été étudiées. La chromatographie de gel par exclusion montre la présence d'agrégat protéique, pouvant ètre stabilisé du point de vue hydrophobique. Des différences entre les fractions protéiques solubles sont observées par électrophorèse. L'analyse en acides aminés des deux fractions protéiques montre une différence marquée en proline. Il semble que cet acide aminé nonpolaire est au moins partiellement responsable de la solubilité inhabituelle de la matri e de l'émail.
Zusammenfassung
Die Matrix von Rinderzahnschmelz ist in gewissen organischen Lösungsmitteln teilweise löslich. In der Annahme, daß dieses Verhalten auf der Anwesenheit von Lipiden beruht, wurden die Neutrallipide des Schmelzes untersucht. Es war möglich, vor der Entkalkung des Gewebes 44% der totalen neutralen Lipidkomponente zu entfernen. Cholesterolester, Triglyceride und freie Fettsäuren überwogen in diesen Lipiden. Nach Entkalkung des Schmelzes wurden die übrigen Lipide freigesetzt. Die Zusammensetzung der Lipide in diesem Extrakt war der ersten ähnlich. Die Gesamtmenge der Lipide aus dem Zahnschmelz war jedoch ungenügend, um eine Lipophylie gestützt auf die Lipoproteinbildung zu erklären. Anschließend wurden die Proteine dieses Gewebes untersucht. Das Vorkommen von Proteinaggregaten, möglicherweise hydrophob stabilisiert, konnte durch Gelfiltration gezeigt werden. Mittels Elektrophorese konnten Unterschiede zwischen löslichen und unlöslichen Proteinfraktionen nachgewiesen werden. Ein deutlicher Unterschied im Prolingehalt dieser beiden Proteinfraktionen zeigte sich bei der Aminosäurenanalyse. Aus diesen Resultaten wurde geschlossen, daß diese nicht-polare Aminosäure zum mindesten teilweise für die außergewöhnlichen Löslichkeitseigenschaften der Zahnschmelzmatrix verantwortlich ist.
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This investigation was supported by the National Institute of Dental Research USPHS DE-02623.
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Fincham, A.G., Burkland, G.A. & Shapiro, I.M. Lipophilia of enamel matrix. Calc. Tis Res. 9, 247–259 (1972). https://doi.org/10.1007/BF02061965
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DOI: https://doi.org/10.1007/BF02061965