Verniquet F, Gaillard J, Neuburger M, Douce R
Laboratoire de Physiologie Cellulaire Végétale, CEN-G, DBMS/PCV, Grenoble, France.
Biochem J. 1991 Jun 15;276 ( Pt 3)(Pt 3):643-8. doi: 10.1042/bj2760643.
Preincubation of potato (Solanum tuberosum) tuber mitochondria with 300 microM-H2O2 for 10 min nearly stopped the State 3 rate of citrate oxidation. Addition of isocitrate resulted in resumption of O2 uptake. The State 3 rates of succinate, external NADH and 2-oxoglutarate oxidation were unaffected by H2O2 over the dose range 50-500 microM. Preincubation of mitochondria with 300 microM-H2O2 for 5 min unmasked in the matrix space a paramagnetic signal with a peak at a g value of approx. 2.03. Aconitase was purified over 135-fold to a specific activity of 32 mumol/min per mg (with isocitrate as substrate) from the matrix of potato tuber mitochondria. The native enzyme was composed of a single polypeptide chain (molecular mass 90 kDa). Incubation of purified aconitase with small amounts of H2O2 caused the build up of a paramagnetic 3Fe cluster with a low-field maximum of g = 2.03 leading to a progressive inhibition of aconitase activity. The results show that aconitase present in the matrix space was the major intramitochondrial target for inactivation by H2O2.
将马铃薯（Solanum tuberosum）块茎线粒体与300微摩尔/升的过氧化氢预孵育10分钟，几乎使柠檬酸氧化的状态3速率停止。加入异柠檬酸后，氧气摄取恢复。在50 - 500微摩尔/升的剂量范围内，过氧化氢对琥珀酸、胞外烟酰胺腺嘌呤二核苷酸（NADH）和2 - 氧代戊二酸氧化的状态3速率没有影响。将线粒体与300微摩尔/升的过氧化氢预孵育5分钟，在基质空间中揭示出一个顺磁信号，其峰值在g值约为2.03处。从马铃薯块茎线粒体基质中纯化出的乌头酸酶比活性提高了135倍以上，达到每毫克32微摩尔/分钟（以异柠檬酸为底物）。天然酶由一条单一的多肽链组成（分子量90千道尔顿）。用少量过氧化氢孵育纯化的乌头酸酶会导致顺磁3铁簇的积累，其低场最大值为g = 2.03，从而导致乌头酸酶活性逐渐受到抑制。结果表明，存在于基质空间中的乌头酸酶是过氧化氢使线粒体内失活的主要靶点。
