Activation of the Alternative Complement Pathway by Water-Insoluble Glucans of Streptococcus Mutans: The Relation between Their Chemical Structures and Activating Potencies

Abstract

Abstract Water insoluble, sticky glucan was synthesized by reacting glucosyltransferase obtained from the culture filtrate of cariogenic Streptococcus mutans OMZ 176 on sucrose. This glucan (OMZ 176 glucan), that consisted of the backbone chains of consecutive α-1,3 glucosidic linkages (65%) and the side chain of α-1,6 glucosidic bonds (35%), showed an ability to activate the alternative pathway of the complement system in human serum. Water soluble glucans synthesized from the reaction of glycosyltransferases of S. mutans strain AHT, FA-I, and Ingbritt with sucrose, that have a high content of α-1,6 and a low content of α-1,3 glucosidic linkages, were less effective to activate the complement system. Sephadex (G-25) and Dextran (T-2,000 and T-40), that consisted exclusively of α-1,6 glucosidic linkages, did not significantly activate the complement system. Controlled Smith degradation products of OMZ 176 glucan, composed of the α-1,3 linked glucose backbone chain alone, lost its activity. From these results it was concluded that both backbone chain of α-1,3 glucose units and branched α-1,6 glucose units were essential for the OMZ 176 glucan to activate the alternative pathway of the human complement system.

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