Schilling K M, Bowen W H
Department of Dental Research, University of Rochester, School of Medicine and Dentistry, New York 14642, USA.
J Dent Res. 1988 Jan;67(1):2-8. doi: 10.1177/00220345880670010201.
This study aimed to determine physical and kinetic properties of glucosyltransferase (GTF) adsorbed onto hydroxyapatite (HA) surfaces. For development of a solid-phase enzyme assay, 4.0-mg samples of washed HA powder were exposed to centrifuged whole saliva (WSHA) or buffer, and subsequently exposed to a GTF solution. The activities of GTF adsorbed to HA and that remaining in solution were measured. WSHA was more effective in adsorbing GTF than was naked HA. Enzyme activity on the surface of WSHA was enhanced; more activity was detected on WSHA than was apparently removed from solution. A similar effect was observed when GTF was adsorbed to naked HA from a mixture with lysozyme or saliva; however, no enhancement was seen when GTF was adsorbed from a mixture with albumin. Compared with GTF in solution, adsorbed GTF displayed activity over a much wider range of pH values. Temperature-activity profiles indicated that GTF adsorbed to surfaces had a lower temperature optimum (40 degrees C) than did soluble enzyme (45 degrees C), and that the bound enzyme was more resistant to adverse effects of heat at elevated temperatures. The majority of glucan made by GTF adsorbed to parotid saliva-coated HA remained attached to the surface. The activity of lysozyme adsorbed to HA was reduced by adsorption of GTF to the same surface and was almost completely abolished by formation of glucans by the adsorbed GTF. These results suggest that soluble bacterial enzymes found in saliva can be incorporated into pellicle, interact with host-derived molecules on the surfaces of teeth, express enzymatic activity, and potentially influence the biological properties of pellicle.
本研究旨在确定吸附在羟基磷灰石（HA）表面的葡糖基转移酶（GTF）的物理和动力学性质。为了开发一种固相酶测定法，将4.0毫克洗涤过的HA粉末样品暴露于离心后的全唾液（WSHA）或缓冲液中，随后再暴露于GTF溶液中。测定吸附到HA上的GTF以及留在溶液中的GTF的活性。WSHA比裸露的HA更有效地吸附GTF。WSHA表面的酶活性增强；在WSHA上检测到的活性比从溶液中明显去除的活性更多。当GTF从与溶菌酶或唾液的混合物中吸附到裸露的HA上时，观察到类似的效果；然而，当GTF从与白蛋白的混合物中吸附时，未观察到增强作用。与溶液中的GTF相比，吸附的GTF在更宽的pH值范围内显示出活性。温度-活性曲线表明，吸附到表面的GTF的最适温度（40℃）低于可溶性酶（45℃），并且结合的酶在升高的温度下对热的不利影响更具抗性。吸附到腮腺唾液包被的HA上的GTF产生的大多数葡聚糖仍附着在表面。吸附到HA上的溶菌酶的活性因GTF吸附到同一表面而降低，并且吸附的GTF形成葡聚糖几乎完全消除了溶菌酶的活性。这些结果表明，唾液中发现的可溶性细菌酶可以整合到获得性膜中，与牙齿表面的宿主衍生分子相互作用，表达酶活性，并可能影响获得性膜的生物学性质。
