Umetsu H, Van Chuyen N
Department of Food and Nutrition, Japan Women's University, Tokyo, Japan.
J Nutr Sci Vitaminol (Tokyo). 1998 Apr;44(2):291-300. doi: 10.3177/jnsv.44.291.
In this study, lysozyme was modified by glucose in the dry state (50 degrees C, RH 75%) and the peptide patterns were investigated using HPLC after hydrolyzing by the pepsin-pancreatin system. Native or modified lysozyme was also administered to rats to clarify digestibility and absorbability in vivo. The digestibility of lysozyme modified by glucose decreased depending on reaction time. In vitro, when lysine residue of lysozyme was modified by glucose at a level of about 50%, the generated peptide patterns with molecular weights (MW) below 3,000 Da were similar to that of native lysozyme, and the yields of peptides from modified lysozyme were lower than those of native lysozyme. However, there are some differences between the hydrolysate patterns of native and modified lysozymes of MW over 10,000 Da, and the yields of these peptides from modified lysozyme are higher than those from native lysozyme. In vivo, the percentage of 30 d-modified lysozyme remaining in rat digestive tracts after 90 min of administration was 11% of the dosage as compared with 0.4% for native lysozyme. However, the digestive peptide patterns of native or modified lysozymes in the rat small intestine were also similar to those of the control. Consequently, it is estimated that modified lysozyme was digested as easily as native lysozyme when the degree of modification of lysine residue by glucose was about 60% even in vivo.
在本研究中，溶菌酶在干燥状态（50℃，相对湿度75%）下用葡萄糖进行修饰，然后通过胃蛋白酶-胰酶系统水解后，使用高效液相色谱法研究肽谱。还将天然或修饰的溶菌酶给予大鼠，以阐明其在体内的消化率和吸收率。葡萄糖修饰的溶菌酶的消化率随反应时间而降低。在体外，当溶菌酶的赖氨酸残基被葡萄糖修饰至约50%的水平时，产生的分子量低于3000 Da的肽谱与天然溶菌酶相似，且修饰溶菌酶的肽产量低于天然溶菌酶。然而，分子量超过10000 Da的天然和修饰溶菌酶的水解产物谱存在一些差异，且修饰溶菌酶的这些肽产量高于天然溶菌酶。在体内，给药90分钟后，30天修饰的溶菌酶在大鼠消化道中残留量占给药剂量的百分比为11%，而天然溶菌酶为0.4%。然而，大鼠小肠中天然或修饰溶菌酶的消化肽谱也与对照相似。因此，据估计，即使在体内，当葡萄糖对赖氨酸残基的修饰程度约为60%时，修饰的溶菌酶与天然溶菌酶一样易于消化。
