Côté G L, Robyt J F
Carbohydr Res. 1984 Apr 2;127(1):95-107. doi: 10.1016/0008-6215(84)85108-3.
An exocellular D- glucansucrase that synthesizes a water-soluble, alpha-D-(1----6)-linked D-glucan having a high proportion of alpha-D-(1----3) branches was purified from the culture broth of Streptococcus mutans 6715. The rate of incorporation of D-[14C]glucose from [14C]sucrose into D-glucan of high molecular weight by this enzyme was increased (stimulated) by the presence of exogenous Leuconostoc mesenteroides B- 512F dextran, and it was found that this dextran could act as an acceptor. A highly branched dextran, containing 45-50% of alpha-D-(1----3) branch linkages, did not stimulate the enzyme nearly so much as B- 512F dextran, which has a low degree (5%) of alpha-D-(1----3) branches. We interpret this as evidence that the stimulating effects of dextran are not due to priming. If they were, the more highly branched dextran should have produced the greatest stimulation per unit weight, because a much greater number of nonreducing-end, priming sites would be available. We show that the D- glucansucrase was capable of transferring D-glucosyl groups from sucrose to B- 512F dextran to form alpha-D-(1----3) branches, thereby rendering the dextran more resistant to hydrolysis by endodextranase . The presence of 1.6M ammonium sulfate caused the enzyme to synthesize a D-glucan having a much higher percentage of alpha-D-(1----3) linkages.
从变形链球菌6715的培养液中纯化出一种胞外D-葡聚糖蔗糖酶，该酶能合成一种水溶性的、α-D-(1→6)连接且α-D-(1→3)分支比例高的D-葡聚糖。外源肠膜明串珠菌B-512F葡聚糖的存在会提高这种酶将[¹⁴C]蔗糖中的D-[¹⁴C]葡萄糖掺入高分子量D-葡聚糖的速率（受到刺激），并且发现这种葡聚糖可以作为受体。一种高度分支的葡聚糖，含有45%-50%的α-D-(1→3)分支键，其对该酶的刺激作用远不如B-512F葡聚糖，后者的α-D-(1→3)分支程度较低（5%）。我们将此解释为葡聚糖的刺激作用并非由于引发作用的证据。如果是引发作用，那么分支程度更高的葡聚糖每单位重量应产生最大的刺激作用，因为会有更多数量的非还原末端引发位点。我们表明，D-葡聚糖蔗糖酶能够将蔗糖中的D-葡萄糖基转移到B-512F葡聚糖上以形成α-D-(1→3)分支，从而使葡聚糖更耐内切葡聚糖酶水解。1.6M硫酸铵的存在使该酶合成的D-葡聚糖中α-D-(1→3)连接的百分比更高。
