Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, Japan.
J Agric Food Chem. 2010 Mar 10;58(5):2923-30. doi: 10.1021/jf9042997.
We have previously reported that the solubility of French bean 7S globulin (phaseolin) at low ionic strength and its emulsifying stability are remarkably high compared with those of 7S globulins prepared from other plant species, including soybean (Kimura et al. J. Agric. Food Chem. 2008, 56, 10273-10279). In this study, we examined the role of carbohydrate moieties in the properties of phaseolin. Three preparations of phaseolin were analyzed: (i) N7S, prepared from defatted seed meal and having intact carbohydrate moieties; (ii) R7S, expressed in E. coli and lacking N-linked glycans; and (iii) EN7S, having partial N-linked glycans after treatment with Endo H. The solubilities of N7S and EN7S were much higher than that of R7S at a low ionic strength (micro = 0.08). N7S exhibited good emulsifying ability under the conditions examined, but R7S did not. In terms of emulsion stability, an emulsion of R7S separated into two phases after 1 h at micro = 0.01, 0.08, and 0.5, whereas the emulsion of N7S was stable for 5 days at micro = 0.01 and for at least 10 days at micro = 0.08 and 0.5. The emulsion stability of EN7S was comparable to that of N7S under most conditions examined. These results indicate the carbohydrate modifications are necessary for the good solubility, emulsifying ability, and emulsion stability of phaseolin. Further, a structural analysis of the carbohydrate moieties indicates that truncated carbohydrate moieties are sufficient for conferring these physicochemical properties to phaseolin.
我们之前曾报道过，与其他植物来源的 7S 球蛋白（如大豆球蛋白）相比，法国菜豆 7S 球蛋白（伴球蛋白）在低离子强度下的溶解度及其乳化稳定性非常高（Kimura 等人，J. Agric. Food Chem. 2008, 56, 10273-10279）。在这项研究中，我们研究了碳水化合物侧链在伴球蛋白性质中的作用。对三种伴球蛋白制剂进行了分析：（i）N7S，由脱脂豆粉制备，具有完整的碳水化合物侧链；（ii）R7S，在大肠杆菌中表达，缺乏 N 连接聚糖；（iii）EN7S，用内切糖苷酶 H 处理后具有部分 N 连接聚糖。在低离子强度（微 = 0.08）下，N7S 和 EN7S 的溶解度远高于 R7S。N7S 在研究条件下表现出良好的乳化能力，但 R7S 没有。就乳化稳定性而言，R7S 乳液在微 = 0.01、0.08 和 0.5 下 1 小时后分成两相，而 N7S 乳液在微 = 0.01 下稳定 5 天，在微 = 0.08 和 0.5 下至少稳定 10 天。EN7S 的乳化稳定性在大多数研究条件下与 N7S 相当。这些结果表明碳水化合物修饰对于伴球蛋白的良好溶解度、乳化能力和乳液稳定性是必要的。此外，碳水化合物侧链的结构分析表明，截短的碳水化合物侧链足以赋予伴球蛋白这些物理化学性质。
