GM1对肌质网Ca~(2+)-ATPase活性及膜流动性的影响

外源性GM1对肌质网Ca2+-ATPase的水解及转运活性都有明显的抑制作用.在GM1浓度为0～8nmol/mg蛋白质范围内抑制作用具有浓度依赖性.当GM1浓度达到8nmol/mg蛋白质时,酶活性受到最大抑制,此时水解活性降低51%,转运活性降低49%.荧光偏振测定结果表明:GM1参入后,肌质网膜流动性降低.

Effect of GM1 on Ca~(2+) -ATPase Activity and Membrane Fluidity of Sarcoplasmic Reticulum

It has been reported that trace amounts of GM3 and GM1 were found in sarcoplasmic reticulum (SR) of rabbit skeletal muscle, and that exogenous GM3 could modulate the conformation and activity of SR Ca 2+ ATPase. The effects of GM1 on the hydrolysis and calcium uptake activity of SR Ca 2+ ATPase were investigated. The results showed that GM1 inhibited not only ATP hydrolysis activity of Ca 2+ ATPase, but also calcium uptake activity of Ca 2+ ATPase, and the inhibition was concentration dependent within the range of 0～8 nmol/mg protein. The maximum inhibition was 51% for hydrolysis activity, and 49% for calcium uptake. The membrane fluidity was also determined with the fluorescent probes of DPH, 2AS, 9AS and 16AP. With the addition of GM1, the membrane fluidity was seen to be decreased, especially in the deeper layer of membrane. The decreased membrane fluidity was positively correlated to the inhibition of Ca 2+ ATPase activity, suggesting that the effect of GM1 on membrane fluidity might be involved in the modulation of Ca 2+ ATPase activity. The antagonistic effect of GM1 to GM3 on SR Ca 2+ ATPase activity is interesting. Further study on this aspect is still in progress.