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51.
Characterization of purified cytochrome b-c1 complex from Rhodopseudomonas sphaeroides R-26 总被引:1,自引:0,他引:1
A highly purified cytochrome b-c1 complex from Rhodopseudomonas sphaeroides R-26 was isolated by a procedure involving Triton X-100 solubilization, calcium phosphate column chromatography, and ammonium sulfate fractionation. The purified enzyme complex contains, in nanomoles/mg of protein, cytochrome b, 8.3; cytochrome c1, 8.3; iron-sulfur protein, 15; phospholipids, 182; and ubiquinone, 5. Four major polypeptides with apparent molecular weights of 48,000, 30,000, 24,000, and 12,000 were detected in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Mr = 48,000 and 30,000 proteins are cytochromes b and c1, respectively. The enzyme complex catalyzes electron transfer from ubiquinol to cytochrome c with a specific activity of 12.6 mumol of cytochrome c reduced per min/mg of protein at 23 degrees C. This is lower than that of the mitochondrial enzyme, although both systems have similar essential redox components and a similar Km for ubiquinol. The activity is fully sensitive to antimycin A and 5-n-undecyl-6-hydroxy-4, 7-dioxobenzothiazole. The enzyme complex is stable at neutral pH and at lower temperatures, but became less stable when the incubation temperature was raised. At 37 degrees C, the half-life is 15 min. The enzymatic activity was insensitive to treatment with N',N'-dicyclohexylcarbodiimide. No p-chloromercuriphenylsulfonate-alkylable sulfhydryl groups were detected. The major phospholipids associated with the purified enzyme complex are phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol with molar per cent distributions of 25, 21, and 35, respectively. About 60% of the enzymatic activity was abolished upon treatment with phospholipase A2. The phospholipase A2-inactivated activity can be partially restored by the addition of EDTA followed with phospholipids prepared from either the cytochrome b-c1 complex of the same source or a mixture of phosphatidylglycerol and asolectin.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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水稻叶片中存在着氨肽酶,其最适反应pH和最适反应温度分别为8.2℃和40℃,酶促反应的产物量在最初30min内与时间呈直线相关。 水稻叶片衰老过程中叶绿素和蛋白质含量下降,而氨肽酶比活上升;用植物激素延缓或促进叶片衰老蛋白质降解的同时也抑制或促进了氨肽酶比活的上升,说明氨肽酶在水稻叶片衰老蛋白质降解过程中起一定的作用。根据水稻叶片衰老过程中大分子化合物和叶片外部形态的变化,可将叶片衰老过程划分为缓衰期、急衰期和竭衰期。 相似文献
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Eight flavonoids, four 6-oxygenated flavones, two methyl ethers of luteolin, apigenin 6,8-C-diglucoside and quercetin 3-O-glucoside,
were isolated fromNama lobbii andN. rothrockii, sole members of sects.Arachnoidea andCinerascentia, respectively. Both taxa diverge markedly from other namas in morphology and chromosome number and their placement inNama has been questioned. The occurrence of 6-oxygenated flavones in these taxa adds to their already distinctive nature. Flavonoid
evidence argues that both are more closely allied toEriodictyon than either is toNama. 相似文献
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A c-type cytochrome from Hydrogenomonas eutropha was purified 150-fold by butanol extraction, ammonium sulfate precipitation, and column chromatography. Three distinct c-type cytochromes were recovered which did not bind with either carbon monoxide or cyanide and hence did not appear to be denatured. Polyacrylamide gel electrophoresis indicated that one protein was acidic and the other two were basic. The acidic cytochrome c had a sedimentation coefficient of 3.46. Its amino acid composition was not markedly different from other bacterial cytochromes, but relative to mammalian cytochromes c it was low in lysine, threonine, and isoleucine and high in alanine and valine. 相似文献
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<正> 胎盘型碱性磷酸酶(P-ALP)是碱性磷酸酶(EC3.1.3.1.ALP)的一种同工酶。P-ALP除出现于妊娠妇女血清外,一些学者还从恶性肿瘤患者血清中发现此酶,并证明它是一种特异性较强的肿瘤标志物。据此,建立P-ALP的简易纯化方法,制备纯度较高的酶制品是建立P-ALP灵敏的微量检测法的先决条件。本文报道以L-苯丙氨酸(L-phe)为配基,用氯代环氧丙烷活化Sepharose 4B的亲和层析法,从人胎盘纯化P-ALP,并对其部分性质进行了研究。 相似文献