正丁醇对钠钾ATP酶的影响

正丁醇对钠钾ATP酶的影响在不同温度表现不同,在膜的相交温度以下,主要为激活(正丁醇浓度小于0.3克分子浓度),但在膜相交温度以上,正丁醇对酶活力主要起抑制作用.正丁醇对钠钾ATP酶的部分活力——对硝基酚磷酸酯酶活力仅起抑制作用,低温也不激活,这与对硝基酚磷酸酯酶活力的Arrhenius作图没有折点是一致的。实验提示在低温时与钠钾离子传送有关的构象变化是整个反应的限速因素,实验表明,利用正丁醇对膜脂进行微扰可以有助于了解钠钾ATP酶的作用原理。     

兔肌线粒体甘油-3-磷酸脱氢酶的提纯与性质

本文证明兔肌线粒体甘油-3-磷酸脱氢酶(E.C.1.1.99.5)经Triton X-100增溶、羟基磷灰石与DEAE-Sepharose CL6B柱层析和蔗糖密度梯度超离心,得到电泳纯的酶制剂,比活力提高200倍,总活力回收为10％。酶蛋白多肽链的表现分子量为69000。酶-TritonX-100复合物的Stockes′半径为59(?)。沉降系数为10.7s。每毫克蛋白含1.7mg TritonX-100和26μg磷脂。酶在410nm和460nm处有两个吸收峰,分别为非血红素铁和FAD。底物甘油-3-磷酸可大大降低这两个吸收峰值。     

PURIFICATION AND SOME PROPERTIES OF GLYCEROL-3-PHOSPHATE DEHYDROGENASE FROM RABBIT SKELETAL MUSCLE MITOCHONDRIA

Glycerol-3-phosphate dehydrogenase (E. C. 1. 1. 99. 5) was solubilized from rabbit skeletal muscle mitochondria by Triton X-100 and purified through hydroxyapatite column chromatography, DEAE-Sepharose CL-6B column chromatography and sucrose density gradient ultracentrifugation. The preparation was electrophoretically pure, the total recovery was 10% and the specific activity had been increased 200-fold. The apparent molecular weight of the enzyme polypeptide was 69,000, it existed in the form of enzyme-Triton X-100 complex with a Stokes' radius of 59 and a sedimentation coefficient of 10.7S. There were 1.7mg Triton X-100 and 26 μg phospholipid per mg protein of the preparation. The enzyme absorbed at 410 and 460 nm which could be attributed to non-haem iron and FAD respectively. Both of the absorption would be largely diminished by adding the substrate glycerol-3-phosphate.     

SPECTRA PROPERTIES OF RAT LIVER MITOCHONDRIAL CHOLINE DEHYDROGENASE

Choline dehydrogenase contains the prosthetic group FAD, non-haem iron and acid labile sulfur. However, the absorption spectra of the purified enzyme do not change after adding substrate. The reduced absorption spectra of choline dehydrogenase can only be determined after the addition of dithionite. Those choline dehydrogenases situated in the mitochondrial inner membrane can be reduced by substrate and exist in the reduced state. When cholate was used to solubilize the substrate-reduced choline dehydrogenase, the reduced spectra will gradually disappear. However, if solubilization is carried out under anaerobic conditions, the reduced spectra can be retained, suggesting that the solubilized choline dehydrogenase can use oxygen as an acceptor.     

鼠肝线粒体胆碱脱氢酶的光谱性质

胆碱脱氢酶是一个含有辅基FAD,非血红素铁和酸不稳定硫的脱氢酶。然而,底物的加入却不引起纯化的胆碱脱氢酶吸收光谱的变化,只有在加入连二亚硫酸钠后,才能测到胆碱脱氢酶的还原吸收光谱。线粒体内膜上的胆碱脱氢酶能被底物还原而处于还原状态,若用胆酸增溶已被底物还原的胆碱脱氢酶,则原来的还原型光谱也会逐步消失。然而,如果增溶在无氧条件下进行,则还原型光谱可以保持不变;提示增溶的胆碱脱氢酶可以氧直接作为受体。