Kopec Leslie K, Vacca Smith Anne M, Wunder David, Ng-Evans Linda, Bowen William H
Center for Oral Biology, University of Rochester, NY 14624, USA.
Caries Res. 2002 Mar-Apr;36(2):108-15. doi: 10.1159/000057868.
Glucosyltransferase (GTF) plays an essential role in the formation of the biofilm known as dental plaque and in the pathogenesis of dental caries. Mutans streptococci produce at least three distinct GTFs (GtfB, C and D), each of which forms a glucan polymer from sucrose. Glucan is a major constituent of plaque biofilm. GTF adsorbed to a surface forms glucans that differ in structure from those formed by the same enzyme in solution. In the present study, activities of GtfB and GtfC in solution or adsorbed on a surface were inhibited in the presence of a polyclonal antiserum (DS-1) to a mixture of GTFs and by immunoglobulin G (IgG) prepared from DS-1; in contrast, enzyme activity was enhanced by normal rabbit serum (NRS) and IgG from NRS. GtfD activity on a surface was enhanced by both antiserum DS-1 and NRS, and IgG prepared from either serum; GtfD activity in solution was slightly inhibited by each of the sera. The structure of GtfB and GtfC glucans formed in the presence of antiserum differed from that of controls based on linkage analyses, and on their susceptibilities to the glucanohydrolases mutanase (alpha-1,3 hydrolase) and dextranase (alpha-1,6 hydrolase); soluble products from the enzymatic digestion also differed. The results show that the effects of antibody on enzyme activity are more complex than simple inhibition or enhancement and that the presence of antibody may influence glucan structure, which clearly could impact plaque formation. The results have implications for the formation and properties of biofilms formed in other environments.
葡糖基转移酶（GTF）在称为牙菌斑的生物膜形成以及龋齿发病机制中起着至关重要的作用。变形链球菌产生至少三种不同的GTF（GtfB、C和D），每种GTF都能从蔗糖形成葡聚糖聚合物。葡聚糖是菌斑生物膜的主要成分。吸附在表面的GTF形成的葡聚糖在结构上与溶液中同一酶形成的葡聚糖不同。在本研究中，针对GTF混合物的多克隆抗血清（DS-1）以及由DS-1制备的免疫球蛋白G（IgG）可抑制溶液中或吸附在表面的GtfB和GtfC的活性；相比之下，正常兔血清（NRS）和来自NRS的IgG可增强酶活性。抗血清DS-1和NRS以及由任一血清制备的IgG均可增强表面GtfD的活性；溶液中GtfD的活性受到每种血清的轻微抑制。基于连接分析以及它们对葡聚糖水解酶变聚糖酶（α-1,3水解酶）和右旋糖酐酶（α-1,6水解酶）的敏感性，在抗血清存在下形成的GtfB和GtfC葡聚糖的结构与对照不同；酶消化产生的可溶性产物也不同。结果表明，抗体对酶活性的影响比简单的抑制或增强更为复杂，并且抗体的存在可能影响葡聚糖结构，这显然会影响菌斑形成。这些结果对在其他环境中形成的生物膜的形成和特性具有启示意义。
