Rapid inactivation of plant aconitase by hydrogen peroxide.
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.
Verniquet
F
F
Laboratoire de Physiologie Cellulaire Végétale, CEN-G, DBMS/PCV, Grenoble, France.
Gaillard
J
J
Neuburger
M
M
Douce
R
R
D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation / Q000187:drug effects; D005290:Ferric Compounds / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011198:Solanum tuberosum / Q000187:drug effects / Q000201:enzymology*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000187:drug effects
D002951:Citrates; D005290:Ferric Compounds; D006861:Hydrogen Peroxide; D000154:Aconitate Hydratase; D010100:Oxygen