摘要
丙酮酸氧化酶既能被两性脂类激活,也能被蛋白酶从羧基端切下一个23肽(称α-肽)激活,而且这两种激活方式相互排斥。本文用分离纯化的α-肽,通过测定色氨酸荧光能量转移的方法,证明α-肽能与磷脂囊(vesicle)结合。我们选用两种不同类型的荧光探针,发现α-肽对它们表现不同的色氨酸能量转移效率。α-肽对Dan-syl-DPPE为7.4±1.0％对Dansyl-UAPC为12.5±2.0％。由此推测α-肽的色氨酸残基易与磷脂双层内部疏水区结合,说明α-肽是一种较为疏水的肽。我们推测α-肽在这种外膜酶的激活过程中,提供了与膜结合的部位,在生理过程中起着重要作用。
Pyruvate oxidase is an E.Coli peripheral membrane flavoprotein which can be activated either by binding to lipid amphiphiles or by limited protease digestion. The a-peptide of pyruvate oxidase is a 23 residue peptide which is cleaved from the carboxy terminus of the enzyme during proteolytic activation by chymotrypsin. Cleavage of a-peptide results in the loss of the affinity lipid binding site in the enzyme. In this paper we have studied the binding of the a-peptide to phospholipid vesicles by tryptophan fluorescence energy transfer measurements. We used two kinds of different fluorescence probes.The efficiency of energy transfer from a-peptide to Dan-syl-DPPE is 7.4±1.0% and to Dansyl-UAPC is 12.5±2.0%. These Results indicate that the a-peptide tryptophan residue is bound closer to the hydrophobic interior of the phospholipid bilayer.It would appear that the a-peptide is a more hydrophobic peptide. We conclude from these results that the a-peptide furnishes the membrane-binding site in the activation of the peripheral membrane enzyme.
关键词
丙酮酸氧化酶
α-肽
磷脂囊
Pyruvate oxidse, α-Peptide, Phospholipid vesicles, Fluorescence energy transfer
