Sharma M, He Q Y, Tomasz M
Department of Chemistry, Hunter College, City University of New York, New York 10021.
Chem Res Toxicol. 1994 May-Jun;7(3):401-7. doi: 10.1021/tx00039a018.
Mitomycin C (MC), a clinically used antitumor antibiotic, is known to alkylate DNA monofunctionally, and to generate DNA interstrand cross-links by bifunctional alkylation. Both processes are dependent on the reductive activation of MC. Glutathione (GSH) was shown here to cause three types of changes in the pattern of alkylation of DNA by MC: (i) GSH caused a decrease of both the overall covalent binding ratio of MC to Micrococcus luteus DNA and the extent of interstrand cross-linking of 32P-pBR322 DNA, as the concentration of GSH was increased in the reaction media. Approximately 50% inhibition of cross-linking was observed at 20 mM GSH. It is likely that the inhibition is caused by the formation of MC-GSH conjugates competing with DNA alkylation, since both processes are triggered by reductive activation of MC [Sharma, M., and Tomasz, M. (1994) Chem. Res. Toxicol. (preceding paper in this issue)]. (ii) GSH causes a switch from monofunctional to bifunctional activation of MC by the prototype "monofunctional" MC-activating agents H2/PtO2 and NADPH:cytochrome c reductase/NADPH. This was seen by the predominance of bisadducts (i.e., cross-linked adducts) instead of the usual monoadducts in the enzymatic digests of MC-DNA complexes formed in the presence of GSH, as analyzed by HPLC. This finding suggests that GSH participates in the bifunctional activation of MC in vivo. (iii) A ternary MC-GSH-DNA adduct (6) was formed in the presence of GSH both with M. luteus DNA and with a synthetic duplex oligonucleotide; in this adduct the mitosene C1 is linked to N2 of guanine and the mitosene C10 is linked to GSH via sulfur.(ABSTRACT TRUNCATED AT 250 WORDS)
丝裂霉素C（MC）是一种临床使用的抗肿瘤抗生素，已知其可单功能烷基化DNA，并通过双功能烷基化产生DNA链间交联。这两个过程都依赖于MC的还原激活。本文表明，谷胱甘肽（GSH）会导致MC对DNA的烷基化模式发生三种类型的变化：（i）随着反应介质中GSH浓度的增加，GSH会使MC与藤黄微球菌DNA的总体共价结合率以及32P-pBR322 DNA的链间交联程度均降低。在20 mM GSH时观察到交联抑制约50%。这种抑制可能是由于形成了与DNA烷基化竞争的MC-GSH缀合物，因为这两个过程都是由MC的还原激活引发的[沙玛，M.，和托马兹，M.（1994年）《化学研究毒理学》（本期前一篇论文）]。（ii）GSH会使原型“单功能”MC激活剂H2/PtO2和NADPH：细胞色素c还原酶/NADPH对MC的激活从单功能转变为双功能。通过高效液相色谱分析在GSH存在下形成的MC-DNA复合物的酶消化物中，双加合物（即交联加合物）而非通常的单加合物占优势可以看出这一点。这一发现表明GSH在体内参与了MC的双功能激活。（iii）在GSH存在下，与藤黄微球菌DNA和合成双链寡核苷酸均形成了三元MC-GSH-DNA加合物（6）；在该加合物中，丝裂烯C1与鸟嘌呤的N2相连，丝裂烯C10通过硫与GSH相连。（摘要截取自250字）
