大鼠肝乳酸脱氢酶与磷脂脂质体的相互作用

以荧光光度法研究了大鼠肝ＬＤＨ－Ｍ４与磷脂脂质体的相互作用。磷脂脂质体对ＬＤＨ－Ｍ４具有抑制作用。磷脂酰肌醇（ＰＩ）脂质体的作用比磷脂酰乙醇胺（ＰＥ）大。当磷脂／蛋白（Ｗ／Ｗ）比为６时，ＰＩ能完全抑制ＬＤＨ的活性，抑制作用呈剂量效应。而磷脂酰乙醇胺，当其磷脂／蛋白（Ｗ／Ｗ）比超过２时，抑制作用不明显，抑制作用呈非剂量效应。当以２８０ｎｍ为激发波长时，ＬＤＨ－Ｍ４的发射峰为３４５ｎｍ，主要为色氨酸的

Interaction of Rat Liver Lactate Dehydrogenase with Phospholipid Liposomes

In this experiment, we studied the interaction of phospholipid liposomes with the purified LDH-M4 by determining the changes of the enzyme intrinsic fluorescence. Phospholipid liposomes could inhibit the activity of LDH-M4. The effects of phosphatidylinositol (PI) liposome were stronger than those of phosphatidylethanolamine (PE) liposome. PI liposome could completely inhibit the enzyme activity when lipid/protein ratio (W/W) was 6, showing dose-dependent relation.However, the PE liposome had no effects on the enzyme activity when lipid/protein ratio surpassed 2, showing dose-independent relation. The emission maximum wavelength of LDH-M4 was 345 nm when excited by wavelength 280 nm, and it Was predominantly tryptophan fluorescence. Liposomes decreased intrinsic fluorescence intensity of the enzyme and shifted the emission maximum wavelength to higher values.The effects of PI liposome were stronger than those of PE liposome.NaCl solution decreased the effects of liposomes on the emzyme fluorescence. Those results indicate that the electrostatic interaction between liposomes and the enzyme was dominant. The machanism of fluorescence quenching was predominantly static quenching, i.e. the enzyme binding to the liposomes formed a nonfluorescent complex, causing a change in the conformation of the enzyme and decreasing the enzymatic activity.