Effects of chemical modification of lysine residues on the sweetness of lysozyme
Effects of chemical modification of lysine residues on the sweetness of lysozyme
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DOI：
10.1093/chemse/bji021
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发表时间：
2005-03-01
期刊：
影响因子：
3.5
通讯作者：
Kitabatake, N
中科院分区：
文献类型：
--
作者：
Masuda, T;Ide, N;Kitabatake, N
溶菌酶是一种甜味蛋白，其甜度阈值约为7 μ M。为了阐明赖氨酸残基侧链的碱性对甜度阈值的影响，进行了电荷特异性化学修饰，例如赖氨酸残基的胍基化、乙酰化和磷酸化。感官分析表明，胍基化对溶菌酶的甜度阈值没有影响，而乙酰化和磷酸化使溶菌酶的甜度阈值显著提高。为了详细确认赖氨酸残基中碱性的重要性，使用SP-离子交换柱色谱法进行乙酰化（Ac-）和磷酸吡啶氧基化（PLP-）溶菌酶的纯化。阈值没有改变修改少于两个残基（类似于7 μ M），而阈值显着增加到15和34 μ M时，四-Ac和三-PLP，分别。此外，在30 μ M（六-、五-Ac和四-PLP）下未检测到甜味。应该注意的是，通过酸性磷酸酶去除三-PLP溶菌酶中磷酸基团的负电荷导致甜度的恢复（6.4 μ M），表明赖氨酸残基位置处的碱性是溶菌酶甜度的原因，并且可能需要与其推定受体相互作用的严格电荷互补性。
Lysozyme is a sweet-tasting protein with a sweetness threshold value of around 7 mu M. To clarify the effect of basicity at the side chain of lysine residues on the threshold values of sweetness, charge-specific chemical modifications such as guanidination, acetylation and phosphopyridoxylation of lysine residues were performed. Sensory analysis showed that the sweetness threshold value of lysozyme was not changed by guanidination, whereas it was increased markedly by acetylation and phosphopyridoxylation. To confirm the importance of the basicity in the lysine residues in detail, purification of acetylated (Ac-) and phosphopyridoxylated (PLP-) lysozymes using SP-ion exchange column chromatography was performed. The threshold values were not changed by modification with fewer than two residues (similar to 7 mu M), whereas the threshold values significantly increased to 15 and 34 mu M when tetra-Ac and tri-PLP, respectively. Furthermore, sweetness was not detected at 30 mu M (hexa-, penta-Ac and tetra-PLP). It should be noted that removal of the negative charges of the phosphate groups in the tri-PLP lysozyme by acid phosphatase resulted in the recovery of sweetness (6.4 mu M), indicating that basicity at the position of the lysine residues is responsible for lysozyme sweetness and that strict charge complementarities might be required for interaction to its putative receptor.