NO对银杏悬浮细胞生长及黄酮类物质合成的影响

以硝普钠(sodium nitroprusside,SNP)为一氧化氮(NO)的供体,向银杏悬浮细胞培养液中加入不同浓度的SNP,研究外源NO对银杏悬浮细胞生长状况、过氧化氢酶(CAT)活性、苯丙氨酸解氨酶(PAL)活性和黄酮类物质生物合成的影响.结果表明,低浓度SNP有利于银杏悬浮细胞生长,而高浓度SNP可以促进黄酮类物质的合成.银杏悬浮细胞在添加0.5和10 mmol/L SNP的培养基中培养16 d时,细胞干重分别为对照组的134%和73%;在添加10 mmol/L SNP的培养基中培养20 d时,细胞中黄酮类物质的含量为对照组的136%.同时,10 mmol/L SNP促进银杏悬浮细胞PAL和CAT活性显著升高.NO专一性淬灭剂c-PITO(carboxyl phenyltetramethylimidazoleoxide)抑制SNP对银杏悬浮细胞生长、CAT活性、PAL活性和黄酮类物质含量的促进作用,说明SNP是通过其分解产物NO影响细胞生长和黄酮类物质的合成.根据这些结果推测,NO可能通过触发银杏悬浮细胞的防卫反应,激活了细胞中黄酮类物质的生物合成途径.     

1株褐藻胶降解菌的筛选、鉴定及产酶条件优化

为获得可产生褐藻胶裂解酶并高效降解褐藻胶的菌株,以海藻酸钠为唯一碳源配制培养基,以透明圈法进行初筛,DNS法复筛,从海洋生物中筛选得到1株高酶活力褐藻胶降解菌株B12,经16S rDNA序列分析、生理生化试验、电镜观察,确定该菌为弧菌属(Vibrio sp.).通过单因素试验及响应面优化试验对影响菌株生长和产酶条件的5...     

过量表达异柠檬酸裂解酶对ldh-1谷氨酸棒状杆菌产丁二酸的影响

谷氨酸棒状杆菌SA001是缺失了乳酸脱氢酶基因 (ldhA) 的菌株。为了增加厌氧条件下经异柠檬酸到丁二酸的代谢通量,以提高丁二酸的产量。将来自大肠杆菌Escherichia coli K12的异柠檬酸裂解酶基因导入谷氨酸棒状杆菌SA001 (SA001/pXMJ19-aceA) 中。该菌经0.8 mmol/L的IPTG有氧诱导12 h后,转入厌氧发酵16 h,丁二酸的产量为10.38 g/L,丁二酸的生产强度为0.83 g/(L·h)。与出发菌株比较,异柠檬酸裂解酶的酶活提高了5.8倍,丁二酸的产量提高了48%。结果表明过量表达异柠檬酸裂解酶可以增加由乙醛酸途径流向丁二酸的代谢流。     

Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase

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Transcellular progression of infection threads in Medicago truncatula roots is associated with locally confined cell wall modifications

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A pathway of the autotrophic CO2 fixation in Chloroflexus aurantiacus

Autotrophically grown cells of Chloroflexus aurantiacus B-3 were shown to possess activity of ATP-dependent malate lyase (acetylating CoA). ATP: malate lyase is supposed to be the specific enzyme of the cycle of the autotrophic CO₂ fixation, in which pyruvate synthase, pyruvate phosphate dikinase, phosphoenolpyruvate (PEP) carboxylase and malate dehydrogenase are involved as well. The main product of the CO₂ fixation cycle is glyoxylate, which could further be converted into 3-phosphoglyceric acid (3-PGA) in the reactions of either glycerate or serine pathway. The enzymes of both pathways were detected in C. auratiacus B-3. The results of the in vivo studies of glyxoylate and glycine metabolism, as well as the inhibitor analysis using fluoroacetate (FAc), isonicotinic acid hydrazide (INH), and 4-aminopterin (4-AP) confirm the operation of the proposed pathway in Chloroflexus.Abbreviations 3-PGA 3-phosphoglyceric acid - 4-AP 4-aminopterin - FAc fluoroacetate - INH isonicotinic acid hydrazide - MV methyl viologen - PEP phosphoenolpyruvate - THF tetrahydrofolate - TPP thiamine pyrophosphate     

l-Phenylalanine ammonia lyase from the lignified and non-lignified regions of Cuscuta chinensis

l-Phenylalanine ammonia lyase (PAL) was not uniformly distributed along the length of Cuscuta chinensis vine but showed alternate zones of high and low activities starting from the tip. The first region of high activity, 0–5 cm from the tip, coincided with high protein and soluble phenolic content. The second zone 17.5–30 cm, coincided with the region of lignification in the secondary xylem. PAL occurs as at least two isoenzymes in the tip and lignified regions and these have been partially purified. The properties of PAL from both the lignified and non-lignified regions could not be distinguished by several criteria including rates of in vivo decay following excision of the vine. Some of the properties of the major isoenzyme of PAL from the tip are reported.     

Characterization of Aspergillus nidulans peroxisomes by immunoelectron microscopy

In previous work, we have demonstrated that oleate induces a massive proliferation of microbodies (peroxisomes) in Aspergillus nidulans. Although at a lower level, proliferation of peroxisomes also occurrs in cells growing under conditions that induce penicillin biosynthesis. Here, microbodies in oleate-grown A. nidulans cells were characterized by using several antibodies that recognize peroxisomal enzymes and peroxins in a broad spectrum of eukaryotic organisms such as yeast, and plant, and mammalian cells. Peroxisomes were immunolabeled by anti-SKL and anti-thiolase antibodies, which suggests that A. nidulans conserves both PTS1 and PTS2 import mechanisms. Isocitrate lyase and malate synthase, the two key enzymes of the glyoxylate cycle, were also localized in these organelles. In contrast to reports of Neurospora crassa, our results demonstrate that A. nidulans contains only one type of microbody (peroxisomes) that carry out the glyoxylate cycle and contain 3-ketoacyl-CoA thiolase and proteins with the C-terminal SKL tripeptide. Received: 4 March 1998 / Accepted: 2 July 1998