共查询到20条相似文献，搜索用时 31 毫秒
1.
Inhibition of phosphofructokinase by quinone methide and alpha-methylene lactone tumor inhibitors 总被引：2，自引：0，他引：2
The plant-derived tumor inhibitors taxodone, taxodione, vernolepin, eupacunin, and euparotin acetate each inhibit the sulfhydryl enzyme, phosphofructokinase. The substrates, fructose-6-phosphate and adenosine triphosphate, protect the enzyme from this, inhibition as does the addition of dithiothreitol to the inhibitors. Incubation of taxodione with phosphofructokinase is associated with the loss of about one sulfhydryl group per inhibitor molecule, and the substrates protect six sulfhydryl groups per protomer of 93,000 daltons. 相似文献
2.
An enzyme in extracts of Euglena gracilis splits both purine and pyrimidine internucleotide bonds of ribonucleic acid. Its pH optimum is at 4.5; it is very heat-labile and is rather insensitive to inhibition by metal ions or sulfhydryl group reagents. A partial purification of the enzyme is described. 相似文献
3.
L-Dopa methyl ester: prolongation of survival of neuroblastoma-bearing mice after treatment 总被引：1，自引：0，他引：1
M M Wick 《Science (New York, N.Y.)》1978,199(4330):775-776
L-Dopa has has been shown to demonstrate enhanced toxicity toward melanoma cells in vitro. Since melanocytes arise from the neural crest embryologically, the effect of L-dopa methyl ester, a soluble analog, on the murine C1300 neuroblastoma was studied. There was significant antitumor activity against the neuroblastoma, which was enhanced by combination with a dopa decarboxylase inhibitor, Ro4-4602. In vitro studies suggested inhibition of DNA synthesis as the principal site of action. A mechanism involving sulfhydryl compound scavenging is postulated. 相似文献
4.
D M Norris S M Ferkovich J M Rozental J E Baker T K Borg 《Science (New York, N.Y.)》1970,170(959):754-755
1,4-Naphthoquinones inhibit feeding of Periplaneta americana by complexing with sulfhydryl groups of receptor protein in sensory neurons, by oxidizing the sulfhydryl groups, and by being reduced. 相似文献
5.
为探寻芸豆蛋白加工利用新途径,采用乙酰化处理对芸豆分离蛋白进行改性,通过分析改性过程中芸豆蛋白暴露巯基、游离巯基、二硫键及表面疏水性的变化,探讨乙酰化改性对芸豆分离蛋白凝胶特性的影响。结果表明:1)当乙酸酐与芸豆蛋白质量比为0.2时,蛋白酰化度达到89%,改性过程基本完成,改性后的芸豆分离蛋白在中性条件下(pH6~8)表现出较高的溶解度;2)随乙酰化改性程度的增加,芸豆蛋白总游离巯基的质量摩尔浓度逐渐下降,表面巯基、二硫键的质量摩尔浓度逐渐上升,表面疏水性表现为先下降后上升的趋势。与未改性蛋白相比,乙酰化改性后芸豆分离蛋白的表面巯基的质量摩尔浓度和表面疏水性显著性提高,增强了凝胶形成过程中蛋白质分子相互作用,显著提高了凝胶的硬度、弹性和内聚性。 相似文献
6.
Mercurial-induced transformation of myosin prevented by adenosine triphosphate and pyrophosphate 总被引：1，自引：0，他引：1
D R Kominz 《Science (New York, N.Y.)》1965,149(690):1374-1375
Adenosine triphosphate and pyrophosphate prevent the loss of Ca(//)-activated adenosine triphosphatase activity caused by high concentrations of mercurial sulfhydryl reagent. They concomitantly prevent the transformation of myosin into faster-sedimenting products. This is adduced as support for the hypothesis that the strategic sulfhydryl group is not binding adenosine triphosphate at the active site, but is initiating a conformational change upon its reaction with the mercurial reagent. 相似文献
7.
Heat inactivation of the relaxing site of actomyosin: prevention and reversal with dithiothreitol 总被引：1，自引：0，他引：1
Adenosine triphosphate and magnesium (MgATP) inhibit contraction by binding to a specific relaxing site on natural actomyosin gel. This inhibitory control site is distinct from the active sites where MgATP causes contraction.In high concentrations of MgATP, calcium triggers contraction by releasing the protein from substrate inhibition, allowing the contractile reactions to occur. Heating the protein for 5 minutes at 43 degrees C selectively inactivates the relaxing site. After this treatment, actomyosin with MgATP contracts as well without calcium as with it. That this effect of heat is prevented and reversed by dithiothreitol (an agent that reduces disulfide bonds) indicates that the structure of the relaxing site depends on certain labile sulfhydryl groups, which may be those of tropomyosin. When these are oxidized to disulfide bonds, the site loses its activity; when the disulfide bonds are reduced, the site regains its activity. 相似文献
8.
G M Green 《Science (New York, N.Y.)》1968,162(855):810-811
Phagocytosis of bacteria by rabbit alveolar macrophages is inhibited quantitatively by cigarette smoke in vitro. This phagocytoxic effect was abolished by addition of 0.2 to 0.4 micromole of glutathione or cysteine per milliliter of cigarette smoke. Serum protein was required to obtain both the toxic effect of the smoke and the protective action of the sulfhydryl compounds. The protective role of the sulfhydryl agents suggests an oxidant action of the cigarette smoke on these pulmonary cells. 相似文献
9.
[目的]为延长樱桃的保鲜时间,制得优良的樱桃保鲜剂。[方法]采用固-液反应法制备了巯基化壳聚糖及它们的金属离子配合物,并以壳聚糖的改性材料配制成樱桃保鲜剂,通过对樱桃损耗率、可溶性固形物、可滴定酸、VC含量、呼吸强度的测定研究了不同浓度保鲜剂对樱桃的保鲜效果。[结果]用壳聚糖制备的保鲜剂能有效地延长樱桃的贮藏期,降低贮藏期间樱桃果实的损耗,减缓樱桃可溶性固形物、可滴定酸、VC含量的下降,还能减弱樱桃的新陈代谢。巯基化壳聚糖对于樱桃涂膜保鲜的最优浓度是10 g/L,其保鲜效果在21 d以上;添加金属离子制得的复合保鲜液对樱桃能起到更好的保鲜效果。[结论]巯基化壳聚糖及其金属离子复合物可作为保鲜剂用于樱桃的保鲜。 相似文献
10.
为研究南海鸢乌贼Symplectoteuthis oualaniensis肌原纤维蛋白在加热过程中理化性质的变化,以南海鸢乌贼胴体肌肉为原料,对其肌原纤维蛋白在加热过程中浊度、溶解度、Ca~(2+)-ATPase活性和总巯基(-SH)含量进行了测定,并对该蛋白质在整个加热过程中SDS-PAGE电泳图的变化进行了研究。结果表明:在25~35℃时,鸢乌贼肌原纤维蛋白的浊度、溶解度、Ca~(2+)-ATPase活性、总巯基含量的变化均比较缓慢;在35℃后继续升温,浊度、Ca~(2+)-ATPase活性、总巯基含量均发生明显变化;总巯基含量在40~50℃时出现短暂升高现象后又急剧降低,溶解度在50℃时开始明显降低;在25~35℃时,随着温度的逐渐升高,鸢乌贼肌原纤维蛋白的肌球蛋白重链(MHC)略有减少,副肌球蛋白(PM)和肌动球蛋白(Actin)基本上未发生变化,但在35℃后,鸢乌贼肌原纤维蛋白开始产生大分子物质,逐渐发生变性。 相似文献
11.
Thioglycolic acid neutralized with sodium carbonate, sodium thioglycolate (Eastman), ethyl mercaptan, cysteine hydrochloride and certain sulfur-containing reducing agents (sodium bisulfite and sodium hydrosulfite) antagonize the antibacterial action of 2-methyl-1,4-naphthoquinone on Escherichia coli in a synthetic medium. Other reducing agents such as stannous chloride, potassium formate and sodium thiosulfate, show no such antagonism. The antibacterial activities of 2-methyl-3-chloro-1,4-naphthoquinone and 2,6-dimethyl-1,4-naphthoquinone are also abolished by excess thioglycolate and cysteine, while that of 2-methyl-3-methoxy-1,4-naphthoquinone with -OCH(3) instead of -Cl or -H in the 3 position on the quinone ring, is not. These findings suggest that the mode of antibacterial action of 2-methyl-1,4-naphthoquinone is by blocking essential enzymes through combination with sulfhydryl groups, or through combination with sulfhydryl groups of essential bacterial metabolites. This combination may take place in the 3-position on the quinone ring. This mode of action is similar to that suggested by other investigators for several antibiotic agents including penicillin. The antibacterial activity of the methoxy quinone, however, even in the presence of sulfhydryl groups, suggests that the foregoing explanation may not be the complete one. 相似文献
12.
S Lahiri 《Science (New York, N.Y.)》1981,212(4498):1065-1066
Sulfhydryl reagents cause striking augmentation of the chemoreceptor responses of the carotid body to hypoxia. This indicates that a cellular plasma membrane protein with a reactive sulfhydryl group is a constituent part of the chemoreceptor architecture and provides a means of identification, localization, and isolation of the protein. 相似文献
13.
14.
Acetylcholine receptor: covalent attachment of depolarizing groups at the active site 总被引：8，自引：0，他引：8
Following reduction of the acetylcholine receptor in the electroplax with dithiothreitol, the quaternary ammonium compounds bromoacetylcholine bromide and the p-nitrophenyl ester of (p-carboxyphenyl) trimethylammonium iodide react near the active site probably with a sulfhydryl group. The covalently attached quaternary ammonium moieties additionally interact with the active site noncovalently to activate the receptor and cause depolarization of the cell. 相似文献
15.
I J Chopra 《Science (New York, N.Y.)》1978,199(4331):904-906
Sulfhydryl reagents exert a profound influence on the monodeiodination of thyroxine to triiodothyronine by rat and sheep tissues in vitro. A marked dithiothreitol-induced increase in the monodeiodination by fetal sheep liver homogenates suggests that the characteristically low conversion in fetal tissues is related more to the status of sulfhydryl groups than to a deficiency of the monodeiodinating enzyme. 相似文献
16.
链霉菌分解角蛋白的生化机制研究 Ⅱ角蛋白分解过程中含硫化合物变化规律的初步探讨 总被引：2，自引：0，他引：2
弗氏链霉菌Ｓ－２２１变种在分解利用羽毛角蛋白过程中产生角蛋白酶,使角蛋白不断地降解成多肽或游离氨基酸的同时,角蛋白中的硫也随之转化成巯基化合物、Ｈ２Ｓ和硫酸盐３种含硫化合物形式存在于分解产物中,并对３种含硫化合物形成过程进行了初步探讨。 相似文献
17.
W M Mitchell 《Science (New York, N.Y.)》1968,162(851):374-375
Clostridiopeptidase B, a sulfhydryl protease from Clostridium histolyticum, hydrolyzes the arginylproline bond in the synthetic polypeptide methionyllysyl-bradykinin. Hydrolysis also occurs at a reduced rate at the lysylarginine bond, further delineating the environment necessary for the minor proteolysis seen with this enzyme at lysine residues. The specificity of clostridiopeptidase B differs from trypsin, which hydrolyzes this synthetic polypeptide only at the lysylarginine bond. 相似文献
18.
草鱼肌原纤维蛋白加热过程中理化特性的变化 总被引：5，自引：1，他引：4
考察草鱼肌原纤维蛋白在加热过程中各理化特性的变化规律和机理。结果表明:随着温度的上升,浊度呈S型曲线增加,48℃时上升迅速;黏度呈反S型曲线下降,46℃时下降剧烈;Ca2+-ATPase活性下降,在36～42℃略有上升,46℃时完全失活;总巯基含量从40℃开始显著下降,60～70℃时下降显著。分别于45、55和65℃恒温加热,Ca2+-ATPase活性和黏度随时间延长而下降,浊度上升,温度越高变化越显著;大于50℃恒温加热,总巯基随时间延长而显著下降。草鱼肌原纤维蛋白的DSC扫描图谱在46.37℃和62.59℃出现2个焓变点。SDS-PAGE电泳表明草鱼肌原纤维蛋白在加热过程中(大于45℃)产生了二硫键,说明草鱼肌球蛋白在加热过程中发生了构象变化和分子聚集从而导致了肌原纤维蛋白的热变性。 相似文献
19.
在面包生产中氧化剂常作为面团改良剂来使用。这类氧化剂有碘酸钾、溴酸钾、抗坏血酸、偶氮二甲酰胺和过氧化钙。氧化剂的作用是氧化蛋白质分子中的巯基成二硫键,增强面团筋力,继而提高面团持水性,改善其组织结构,降低粘性,在加工和机械性能方面得以全面改善,生产出高质量的面包。 相似文献
20.
Hydrogen sulfide redtuces the lethal effect of x-rays in dry spores by about 50 percent when given after irradiation, and by approximately 75 percent when present during irradiation. The first effect is the result of removal of radicals that are toxic when combined with oxygen; the second, the removcal of radicals that become toxic in the absence of oxygen. With these results we construct an explanation of the action of sulfhydryl compounds in protection against radiation damage. 相似文献