Flanagan John, FitzGerald Richard J
Department of Life Sciences, University of Limerick, Limerick, Ireland.
J Agric Food Chem. 2002 Sep 11;50(19):5429-36. doi: 10.1021/jf011632n.
Sodium caseinate (NaCN), hydrolyzed with Protamex, a Bacillus proteinase preparation, to 0.5, 1.3, and 17.5% degrees of hydrolysis, was incubated with transglutaminase (TGase) for 3, 42, and 290 min at enzyme/substrate ratios of 1, 1, and 10% (w/w), respectively, pre- and post-hydrolysis. The electrophoretic, reversed-phase high-performance liquid chromatography (RP-HPLC) and nitrogen solubility profiles of the modified products were investigated. Combinations of hydrolysis and incubation with TGase generated products displaying novel physicochemical and nitrogen solubility properties. Significant changes in sodium dodecyl sulfate (SDS) and urea polyacrylamide gel electrophoresis profiles were apparent in the modified caseinate samples. Extensive TGase cross-linking resulted in polymers that were unable to enter the resolving gel during SDS polyacrylamide gradient gel electrophoresis. Extensive combined enzymatic modification resulted in peptides eluting earlier on RP-HPLC than limited combined enzymatic modification or limited hydrolysis. Combination of enzymatic treatments resulted in significantly (P < 0.005) improved solubility around pH 4.6, compared to incubation with TGase or hydrolysis of NaCN alone.
用芽孢杆菌蛋白酶制剂Protamex将酪蛋白酸钠（NaCN）水解至水解度为0.5%、1.3%和17.5%，分别在水解前和水解后，以1%、1%和10%（w/w）的酶/底物比与转谷氨酰胺酶（TGase）孵育3分钟、42分钟和290分钟。对改性产物的电泳、反相高效液相色谱（RP-HPLC）和氮溶解度曲线进行了研究。水解和与TGase孵育相结合产生了具有新型物理化学和氮溶解度特性的产物。在改性酪蛋白酸盐样品中，十二烷基硫酸钠（SDS）和尿素聚丙烯酰胺凝胶电泳图谱有明显变化。广泛的TGase交联导致聚合物在SDS聚丙烯酰胺梯度凝胶电泳过程中无法进入分离胶。与有限的联合酶促修饰或有限水解相比，广泛的联合酶促修饰导致肽在RP-HPLC上洗脱得更早。与单独用TGase孵育或NaCN水解相比，酶处理相结合使pH 4.6左右的溶解度显著提高（P<0.005）。
