Human Topoisomerase I
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Human Topoisomerase I
Human Topoisomerase I is prepared by overexpressing the enzyme in baculovirus-infected insect cells (Spodoptera frugiperda) and purifying it by methods adapted from Stewart et al., 1996. The enzyme is supplied μl in Dilution Buffer.
Store at -80°C. It is recommended that the enzyme is aliquoted to avoid repeated freeze-thaw cycles.
See technical documents below for more detailed information and lot specific activities.
Technical Documents
Human Topoisomerase I Relaxation Assay Kits
These contain the enzyme and the supercoiled DNA substrate in addition to the Assay and Dilution buffers for relaxation reactions. 1 U of human topo I will relax 0.5 µg supercoiled pBR322 DNA in 30 minutes at 37°C.
Technical Documents
Human Topoisomerase I Assay Kits for Cell Extracts
These kits are designed for assaying cell extracts and partially purified fractions containing human topo I. They contain supercoiled DNA substrate, Assay buffer, Dilution buffer and relaxed DNA marker.
The kit components are based on the standard human topo I assay whch contains 500 ng substrate DNA per assay.
Technical Documents
High / Medium-Throughput Assay Kit - Human Topoisomerase I
The kit is supplied with sufficient human topo I enzyme, plasmid DNA substrate, buffers and other assay components* for 100 assays. The enzyme is supplied at a concentration of 10 U/μl in Dilution Buffer. The kit is also supplied with sufficient wash buffers for one 96-well plate. These buffers are supplied as 20X concentrates and must be diluted with ultra pure water prior to use.
More information about this assay can be found on the "Services" page under "High/Medium Throughput Assay".
Kit issued with limited licence for individual use only.
Patent held by Inspiralis Ltd., Norwich, Norfolk, UK. (Patent No. GB0424953.8, US7838230).
Technical Documents
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伊立替康是喜树碱的半合成衍生物。喜树碱可特异性地与拓扑异构酶I结合,后者诱导可逆性单链断裂,从而使DNA双链结构解旋;伊立替康及其活性代谢物SN-38可与拓扑异构酶I-DNA复合物结合,从而阻止断裂单链的再连接。现有研究提示,伊立替康的细胞毒作用归因于DNA合成过程中,复制酶与拓扑异构酶I-DNA一伊立替康(或SN-38)三联复合物相互作用,从而引起DNA双链断裂。哺乳动物细胞不能有效地修复这种DNA双链断裂。
毒理研究
遗传毒性:伊立替康和SN-38在Ames试验中均未显示出致突变性。伊立替康在CHO细胞染色体畸变试验和小鼠微核试验中显示了致断裂作用。
生殖毒性:在啮齿动物多次给药试验中,可见雄性动物生殖器官萎缩。雌性大鼠静脉注射14C一伊立替康,其放射性可透过胎盘屏障,大鼠和家兔试验中,可见本品对胚胎和胎儿的毒性反应。大鼠静脉注射放射性标记的伊立替康后5分钟内,可在其乳汁中检测到放射性,给药4小时后乳汁中药物浓度可达到血药浓度的65倍;雌性大鼠在围产期静脉注射本品可引起仔鼠学习能力和雌鼠仔鼠体重的下降。
尚无足够的和严格控制的孕妇临床研究资料,若患者在孕期使用本品或在使用本品期间怀孕,应被告之对胎儿的潜在危害。有生育可能的妇女在本品给药期间应避免怀孕;母亲在接受本品治疗期间应停止哺乳。
致癌性:尚未进行伊立替康长期给药的致癌性研究,但进行了大鼠连续三周、每周一次静脉注射伊立替康2mg/kg和25mg/kg,然后恢复91周的试验(大鼠静脉注射伊立替康25mg/kg后,其Cmax和AUC分别约相当于人每周给药125mg/m2后的7倍和1.3倍),结果显示,子宫喇叭口处子宫内膜间质息肉和子宫内膜间质肉瘤发生率的增加有明显的剂量依赖性。
【药代动力学】
文献报导,人体静脉注射本品后,伊立替康的血浆浓度呈常指数消除。平均消除半衰期为6~12小时,活性代谢产物SN-3 8的消除半衰期为10~20小时。因为其内酯和羟基酸是化学平衡的,故活性内酯和SN-38的半衰期与完整的伊立替康和SN-38的半衰期相近。
在50~350mg/m2的剂量范围内,伊立替康吸收面积(AUC)与剂量呈线性递增关系:SN-38的AUC增加要小于剂量的增加。在90分钟内静脉滴注本品后1小时内,活性代谢产物SN-38达到最大浓度。伊立替康与血浆蛋白的结合率为 30%~68%,明显低于SN-38与血浆蛋白的结合率(大约95%)。伊立替康主要在肝内由羧酸酯酶转化为活性代谢产物SN-38,后者代谢为葡萄糖甙酸,活性为SN-38的1/50~1/100(由体内细胞毒性检测)。体内分布不明;药物及代谢产物经尿排泄:伊立替康为11%~20%,SN-38<1%,SN-38糖甙约3%。给药48小时后胆汁蓄积和经尿排泄的药25%~50%。
【贮 藏】
遮光,密闭保存。
【包 装】
西林瓶装,1瓶/盒,有40mg及100mg两种规格。
效 期】
24个月
【执行标准】
WS1-(X-166)-2005Z
【生产企业】
企业名称:辉瑞制药;安万特制药;齐鲁制药;江苏恒瑞医药股份有限公司向左转|向右转
B、酶细胞产能细胞内(外)起作用消化酶细胞外起作用B错误;
C、酶同需要适条件同胃蛋白酶与胰蛋白酶所需PH同C错误;
D、葡萄糖细胞质基质解丙酮酸需要酶催化D确.
故选:D.
1970科家致癌RNA病毒发现种特殊RNA病毒聚合酶,该酶能RNA模板,根据碱基互补原则.程与般病毒转录向相反,故称逆转录,催化程酶称逆转录酶,发现哺乳物胚胎细胞裂淋巴细胞含.
逆转录病毒称携带逆转录酶病毒,先侵入宿主细胞病毒RNA模板,靠酶形DNA环化,合宿主细胞染色体原病毒形式宿主细胞代代传.
HIV(艾滋病病毒)典型逆转录病毒
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