Kuramitsu H K, Wondrack L
Infect Immun. 1983 Nov;42(2):763-70. doi: 10.1128/iai.42.2.763-770.1983.
Both dextransucrase and mutansynthetase activities have been purified from the culture fluids of Streptococcus mutans GS-5 (serotype c). Although homogeneous dextransucrase preparations normally synthesize little insoluble glucan, essentially all of the glucan synthesized by this enzyme in the presence of 1.5 M (NH4)2SO4 was water insoluble. Linkage analysis of the insoluble glucans indicated that the presence of NH4+ increased the portion of alpha-1,3-glucose linkages relative to alpha-1,6-glucose units in the product. Chromatofocusing of aggregated glucosyltransferase fractions synthesizing predominantly insoluble glucan yielded primarily dextransucrase activity separable from relatively low levels of mutansynthetase activity. The latter enzyme was detected only in 18-h assays and synthesized primer-dependent insoluble glucan, which was decreased in the presence of NH4+. In the absence of primer dextran T10, the addition of dextransucrase also stimulated insoluble glucan synthesis by mutansynthetase. Dextransucrase and mutansynthetase appear to be distinct enzymes, since the latter possesses a higher molecular weight (155,000 compared to 140,000), a much lower isoelectric point, and did not cross-react with antibody directed against dextransucrase. These results are discussed relative to the mechanism of insoluble glucan synthesis by S. mutans serotype c strains.
变形链球菌GS-5（血清型c）培养液中的葡聚糖蔗糖酶和变聚糖合成酶活性均已得到纯化。尽管纯化的葡聚糖蔗糖酶制剂通常很少合成不溶性葡聚糖，但在1.5M硫酸铵存在下，该酶合成的几乎所有葡聚糖均为水不溶性。对不溶性葡聚糖的键合分析表明，铵离子的存在增加了产物中α-1,3-葡萄糖键相对于α-1,6-葡萄糖单元的比例。对主要合成不溶性葡聚糖的聚集葡糖基转移酶组分进行色谱聚焦，主要得到可与相对较低水平的变聚糖合成酶活性分离的葡聚糖蔗糖酶活性。后一种酶仅在18小时的检测中被检测到，并且合成引物依赖性不溶性葡聚糖，在铵离子存在下其含量会降低。在没有引物葡聚糖T10的情况下，添加葡聚糖蔗糖酶也会刺激变聚糖合成酶合成不溶性葡聚糖。葡聚糖蔗糖酶和变聚糖合成酶似乎是不同的酶，因为后者具有更高的分子量（155,000，而前者为140,000）、更低的等电点，并且与针对葡聚糖蔗糖酶的抗体不发生交叉反应。结合变形链球菌血清型c菌株合成不溶性葡聚糖的机制对这些结果进行了讨论。
