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抗代謝物类化合物具有和体內代謝物(如氨基酸、糖、嘌呤嘧啶、維生素……)相似的結构,相反的生理作用,即为抗代謝物。結构相似是抗代謝物发生抗代謝作用的重要前提,因为:(一)抗代謝物才能和正常代謝物发生竞爭,阻碍体內必需物质的合成,阻碍酶合成对前体的利用,使体內合成的“类生理物质”无生理活性,或使被合成的酶无原来的作用。(二)抗代謝物才能取代酶作用的底质,使酶被占有,无法发揮应有的作用。抗代謝物对肿瘤性生长的抑制常由这两方面解释。 (甲)抗嘌呤嘧啶类: 最早被发現的抗嘌呤化合物是2,6二氨基嘌呤和偶氮烏嘌呤(Azan),临床毒性显著,效果不大。6—巯基嘌呤(6MP)为临床治疗急性白血病的最有效抗嘌呤物。Balis等(1957)发現其对抗腺嘌呤,即在体內轉化为核甙,干扰核酸合成。Henderson发現6MP和硫代烏嘌呤(Thioguanine)合用治疗肿瘤效力增强。
Anti-metabolites have similar structures to the metabolites in the body (such as amino acids, sugars, purine pyrimidines, vitamins ...) and the opposite physiological effect is anti-metabolite. Structural similarity is an important prerequisite for antimetabolite antimetabolism because: (i) antimetabolites compete with normal metabolites, hinder the synthesis of essential substances in the body, hinder the utilization of the enzyme by the precursor, Synthesized within the “physiological class” no physiological activity, or to be synthesized without the original role of the enzyme. (B) anti-metabolites to replace the role of enzyme substrate, the enzyme is occupied, can not play its due role. Inhibition of tumor growth by antimetabolites is often explained by both. (A) Anti-purine pyrimidines: The first anti-purine compounds that were found were 2,6-diaminopurine and Azan, with significant clinical toxicity and little effect. 6-Mercaptopurine (6MP) is the most effective anti-purine in the clinical treatment of acute leukemia. Balis et al (1957) found that it is against adenine, which is converted to nucleoside in the body, interfering with nucleic acid synthesis. Henderson found that combination of 6MP and Thioguanine increases tumor potency.