聚半乳糖醛酸酶（PG2）中色氨酸残基的化学修饰

用化学修饰法以Ｎ－溴代琥珀酰亚胺作修饰剂，对聚半乳糖醛酸酶（ＰＧ２）中色氨酸（Ｔｒｐ）残基与酶活性的关系进行研究，发现１个ＰＧ２分子中有６个Ｔｒｐ残基，其中４个位于酶分子内部，２个位于酶分子表面，该发现通过表面荧光猝灭实验得到进一步证明，酶分子表面的２个Ｔｒｐ残基中，有１个为活性必需的氨基酸，它的修饰导致大部分酶活力丧失，底物保护实验进一步证明该活性必需的Ｔｒｐ可能位于酶的活性部位，酶被修饰后其圆

The Chemical Modification of Tryptophan Residues in Polygalacturonase

The tryptophan residues in polygalacturonase(PG2) had been modified by N-bromosuccinimide(NBS) to study the relationship between the Trp residues and the activity of the enzyme.The results indicate that there are six Trp residues in PG2.Four of them locate in the interior and the other two locate on the surface of the enzyme molecule.One of the Trp residues,which is on the surface of PG2,is essential for the activity of the enzyme and locates at the active site of the enzyme.The spectra of circular dichroism(CD) and fluorescence of PG2 are changed after treatment with NBS.