Yabusaki K K, Ballou C E
Proc Natl Acad Sci U S A. 1978 Feb;75(2):691-5. doi: 10.1073/pnas.75.2.691.
The long-chain polyenoic fatty acids alpha- and beta-paranaric acid form complexes with the 6-O-methylglucose polysaccharide from Mycobacterium smegmatis as demonstrated by an enhanced fluorescence emission of the paranaric acid. This interaction is eliminated by digestion of the methylglucose polysaccharide with alpha-amylase and glucoamylase, which removes four hexose units from the nonreducing end of the chain. Titration of the methylglucose polysaccharide with either paranaric acid isomer suggests formation of a 1:1 complex with a dissociation constant (K(d)) of 0.4 muM. The fluorescence emission of this complex is quenched by palmitoyl-CoA, which indicates that the paranaric acid can be displaced by the acoyl-CoA, a conclusion confirmed by gel filtration. The presumed polysaccharide/palmitoyl-CoA complex has a K(d) of about 0.1 muM. Acoyl-CoA derivatives with shorter fatty acid chains and free palmitic acid complete less effectively, indicating that they form weaker complexes with the polysaccharide. The methylmannose polysaccharides with 12 or 13 sugar units also complex paranaric acid strongly (K(d) approximately 0.4 muM), whereas the isomer with 11 sugar units complexes weakly.The methylglucose polysaccharide has been coupled to L-tryptophan methyl ester. The fluorescence emission spectrum of the attached tryptophan group is shifted to a shorter wavelength relative to N-acetyl-L-tryptophan methyl ester, and this effect is enhanced in the corresponding derivative made with the amylase-digested polysaccharide. The circular dichroism spectrum of the polysaccharide-tryptophan derivative shows three bands with negative ellipticity, in the 270-300 nm region, not observed in the amylase-digested derivative. These results imply that the tryptophan is in a more structured environment in the former than in the latter derivative. alpha-Paranaric acid binds to the polysaccharide-tryptophan conjugate and shows an enhanced fluorescence emission with partial quenching of the tryptophan fluorescence emission, suggestive of Förster energy transfer from tryptophan to paranaric acid.
长链多烯脂肪酸α-和β-副壬酸与耻垢分枝杆菌的6-O-甲基葡萄糖多糖形成复合物，这可通过副壬酸荧光发射增强得以证明。用α-淀粉酶和葡糖淀粉酶消化甲基葡萄糖多糖可消除这种相互作用，这两种酶会从链的非还原端去除四个己糖单元。用任一副壬酸异构体滴定甲基葡萄糖多糖表明形成了1:1复合物，其解离常数（K(d)）为0.4 μM。该复合物的荧光发射被棕榈酰辅酶A淬灭，这表明副壬酸可被酰基辅酶A取代，凝胶过滤证实了这一结论。推测的多糖/棕榈酰辅酶A复合物的K(d)约为0.1 μM。脂肪酸链较短的酰基辅酶A衍生物和游离棕榈酸的作用效果较差，表明它们与多糖形成的复合物较弱。含有12或13个糖单元的甲基甘露糖多糖也能与副壬酸强烈结合（K(d)约为0.4 μM），而含有11个糖单元的异构体结合较弱。甲基葡萄糖多糖已与L-色氨酸甲酯偶联。相对于N-乙酰-L-色氨酸甲酯，连接的色氨酸基团的荧光发射光谱发生蓝移，在用淀粉酶消化的多糖制备的相应衍生物中这种效应增强。多糖-色氨酸衍生物的圆二色光谱在270 - 300 nm区域显示出三条具有负椭圆率的谱带，在用淀粉酶消化的衍生物中未观察到。这些结果表明，与后一种衍生物相比，色氨酸在前一种衍生物中的结构环境更有序。α-副壬酸与多糖-色氨酸缀合物结合，并显示出荧光发射增强以及色氨酸荧光发射部分淬灭，提示存在从色氨酸到副壬酸的福斯特能量转移。
