Pawelczyk T, Olson M S
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760, USA.
Int J Biochem Cell Biol. 1995 May;27(5):513-21. doi: 10.1016/1357-2725(95)00006-b.
The activity of pyruvate dehydrogenase complex purified from pig kidney cortex was affected by various mono- and di-valent ions and changes in ionic strength. The fluorescence emission spectrum of PDC exposed to 0.04 M ionic strength and excited at 280 nm exhibited a maximum at 334 nm; the fluorescence intensity of PDC appeared to depend upon the ionic strength and the K+ and Na+ content of the incubation buffer. Alteration of ionic strength to which the enzyme complex was exposed produced a change in the absorption of the complex at 230 nm. The presence of HPO4(2-) ions prevented changes in the UV absorption spectrum of PDC induced by the variation in ionic strength. The K+ and Na+ ions alone had no effect on the UV spectrum of PDC. Upon increasing the ionic strength to which the enzyme complex was exposed, dramatic changes in the circular dichroism (CD) pattern were observed. At 0.04 M ionic strength PDC exhibited a CD spectrum with minima at 216, 218 and 222 nm and a cross-over point at 215 nm. At 0.15 M ionic strength the CD spectrum of PDC exhibited minima at 223, 226, 228 nm and a cross-over point at 221 nm. The presence of HPO4(2-) ions prevented alterations in the CD spectrum of PDC induced by variations in ionic strength. The K+ and Na+ ions had no effect on the CD spectrum of PDC.
从猪肾皮质中纯化得到的丙酮酸脱氢酶复合体的活性受到各种单价和二价离子以及离子强度变化的影响。暴露于0.04 M离子强度并在280 nm激发的丙酮酸脱氢酶复合体的荧光发射光谱在334 nm处呈现最大值；丙酮酸脱氢酶复合体的荧光强度似乎取决于离子强度以及孵育缓冲液中的K⁺和Na⁺含量。改变酶复合体所暴露的离子强度会导致复合体在230 nm处的吸光度发生变化。HPO₄²⁻离子的存在可防止因离子强度变化而引起的丙酮酸脱氢酶复合体紫外吸收光谱的变化。单独的K⁺和Na⁺离子对丙酮酸脱氢酶复合体的紫外光谱没有影响。随着酶复合体所暴露的离子强度增加，观察到圆二色性（CD）图谱发生了显著变化。在0.04 M离子强度下，丙酮酸脱氢酶复合体呈现出在216、218和222 nm处有最小值且在215 nm处有一个交叉点的CD光谱。在0.15 M离子强度下，丙酮酸脱氢酶复合体的CD光谱在223、226、228 nm处呈现最小值且在221 nm处有一个交叉点。HPO₄²⁻离子的存在可防止因离子强度变化而引起的丙酮酸脱氢酶复合体CD光谱的改变。K⁺和Na⁺离子对丙酮酸脱氢酶复合体的CD光谱没有影响。
