长半衰期重组人超氧化物歧化酶的研制及性质

一种双亲有机化合物聚苯乙烯马来酸丁酯(SMA)经酰胺键与重组人铜锌超氧化物歧化酶(rhCu/Zn SOD)共价交联,制得修饰酶.当42%游离氨基被修饰时,保留酶活力为88%.酶蛋白主链结构在修饰前后变化不大.与天然酶相比,修饰酶的生物半衰期延长了22倍,抗蛋白水解酶能力亦有所增强.     

Biological Reduction of Aromatic Nitroso Compounds: Evidence for the Involvement of Superoxide Anions

The in vitro formation of phenylhydronitroxide and 2-methylphenylhydronitroxide free radicals from nitrosobenzene (NB) and 2-nitrosotoluene (NT), respectively, in either red blood cells (RBC) or RBC hemolysates, was confirmed by electron spin resonance spectroscopy (ESR). Free radicals were generated nonenzymatically from reaction of the respective nitroso compounds with a number of biological reducing agents as corroborated by model studies of NB or NT with NAD(P)H. Under aerobic conditions, phenylhydronitroxide and 2-methylphenylhydronitroxide underwent a subsequent one-electron transfer to oxygen, which then resulted in the formation of superoxide anion (O₂^-). The latter product was confirmed by the superoxide dismutase (SOD)-inhibitable reduction of cytochrome c (cyt c). Apparently, oxygen is needed for continuous formation of the hydronitroxide radical derivatives. On the other hand, under anaerobic conditions, no phenylhydronitroxide radical was generated from NB in the presence of NADH, but the formation of phenylhydroxylamine from NB was detected by the absorption spectrometry. These results suggest that oxygen is a preferential electron acceptor for hydronitroxide radical derivatives.     

Chromatographic properties of the cadmium induced SOD isoform in Rhizopogon roseolus

Exposure of Rhizopogon roseolus mycelia to 15 mmol·dm⁻³ cadmium for 24 h induces a different pattern of Mn-SOD on polyacrylamide gels, probably being a changed form of an originally existing one. The presence of cadmium affects the chromatographic properties of this enzyme and its mobility through the acrylamide gel. This new isoform was purified using DEAE Trisacryl chromatography. Cadmium induced isoform adsorbed stronger to the ligands and was eluated with a Tris-HCl buffer containing 0.1 mol·dm⁻³ NaCl. SOD from control samples (not treated with cadmium) was eluated with the same buffer without NaCl.     

Possible mechanism of captopril induced endothelium-dependent relaxation in isolated rabbit aorta

The mechanism of captopril, an angiotensin converting enzyme (ACE) inhibitor with sulfhydryl group (SH) in its structure, to produce an endothelium-dependent vasorelaxation was studied. In rabbit aorta with intact endothelium and precontracted with phenylephrine, captopril and superoxide dismutase (SOD) produced dose-dependent relaxation. Lisinopril, an ACE inhibitor without a -SH group in its structure, did not produce endothelium-dependent relaxation. It was observed that captopril, like SOD, produced the relaxation by protecting the EDRF from getting inactivated by superoxide anions as pyrogallol and methylene blue inhibited both the captopril and SOD-mediated relaxation. The free radical scavenging action of captopril is further substantiated by the observation that captopril, but not lisinopril, inhibited FeCl₃/ascorbic acid-induced lipid peroxidation in whole tissue homogenates of rabbit aorta to a level comparable to that of SOD. These results suggest that endothelium-dependent vasodilation produced by captopril may be due to its ability to scavenge superoxide anion and this property may be ascribed to the -SH group present in its structure.     

Formation of lipid peroxides in isolated rat liver microsomes by singlet molecular oxygen.

Rat liver microsomes were incubated in neutral aqueous solution of potassium peroxychromate, a system which generates singlet molecular oxygen. Such incubation resulted both in a rapid decline in NADPH-cytochrome c reductase activity, and in an increase in formation of lipid peroxides. These reactions were not inhibited by either superoxide dismutase (SOD) or mannitol, nor were they entirely duplicated by incubating microsomes with hydrogen peroxide. However, a high concentration of 1,4-diazabicyclo-[2,2,2]octane (DABCO), a known scavenger of singlet oxygen, prevented both decline in reductase activity and formation of lipid peroxides. These results suggest that the observed effects are, in fact, attributable to singlet oxygen, and not to hydrogen peroxide, superoxide radical, or hydroxyl radical.     

Superoxide dismutase does not inhibit the oxidation of cytochrome c and cytochrome oxidase.

An electrometric system was used to measure Ca⁺⁺ uptake by sarcoplasmic reticulum vesicles (SR). The method permits continuous recording of Ca⁺⁺ uptake and thus the valuation of kinetic parameters. Furthermore, the ultrasensitivity of the method permits to follow changes in Ca⁺⁺ concentration below 10^?6 M.     

Leukotriene B4, C4, D4 and E4 inactivation by hydroxyl radicals

Leukotriene B4 chemotactic activity and leukotriene C4, D4 and E4 slow reacting substance activity were rapidly decreased by hydroxyl radicals generated by two different iron-supplemented acetaldehyde-xanthine oxidase systems. At low Fe2+, leukotriene inactivation was inhibited by catalase, superoxide dismutase, mannitol and ethanol, suggesting involvement of hydroxyl radicals generated by the iron-catalyzed interaction of superoxide and H2O2 (Haber-Weiss reaction). Leukotriene inactivation increased at high Fe2+ concentrations, but was no longer inhibitable by superoxide dismutase, suggesting that inactivation resulted from a direct interaction between H2O2 and Fe2+ to form hydroxyl radicals (Fenton reaction). The inactivation of leukotrienes by hydroxyl radicals suggests that oxygen metabolites generated by phagocytes may play a role in modulating leukotriene activity.     

Estrogen regulation of superoxide dismutase in normal rat mammary tissues and mammary tumors

Multiple electrophoretic molecular variants of superoxide dismutase were demonstrated in normal rat mammary tissues and DMBA-induced rat mammary tumors. The specific activities of $\text{Cu}\text{Zu}$ superoxide dismutase in mammary tumors of estrogen-treated rats were not significantly different from those activities seen in normal rat mammary tissues. However, the enzyme activities of mammary tumors from untreated rats (no estrogen) were significantly lower than the activities of normal rat mammary tissues. Exogenous estrogen appeared to raise superoxide dismutase levels in DMBA-induced rat mammary tumors to those levels seen in normal rat mammary tissues.     

低pH,铝和钙离子对菌根菌赭丝膜伞的毒性和超氧化物歧化酶的影响

应用急性毒性生物测试方法 ,研究了低 pH和铝离子对菌根菌赭丝膜伞 (Corti nariusrussus)的毒性效应 .试验表明 ,在pH为 6.8、5.5和 4.3,铝离子在低 pH( 4 .3)时对菌根菌毒性最强 ,96hEC50 为 5.0 5mg·L- 1 ,菌根生长受到明显的抑制 ;低 pH和铝离子能诱导菌根菌体内SOD ,与对照组相比 ,菌根菌体内SOD活性明显升高 ;加入钙离子后 ,SOD活性下降 ,并随Ca的投加浓度增加 ,SOD活性逐渐降低 ,表明在低 pH条件下 ,钙离子和铝离子对菌根的影响具有拮抗作用 .     

酵母SOD形成的生理学研究

对筛选出的一株ＳＯＤ高产菌株Ｙ－２１６形成ＳＯＤ的生理条件作了初步研究。结果表明：碳源、氮源、碳氮配比和金属离子等营养条件及培养温度、时间和通气量等培养条件,均对该菌株生物量与ＳＯＤ含量有较大的影响。同时通过对几种酵母的测定,发现酵母菌对氧的抗性越大其ＳＯＤ含量也就越高。