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Redox-dependent modulation of aconitase activity in intact mitochondria.
Biochemistry. 2003 Dec 23; 42(50):14846-55.B

Abstract

It has previously been reported that exposure of purified mitochondrial or cytoplasmic aconitase to superoxide (O(2)(-)(*) or hydrogen peroxide (H(2)O(2)) leads to release of the Fe-alpha from the enzyme's [4Fe-4S](2+) cluster and to inactivation. Nevertheless, little is known regarding the response of aconitase to pro-oxidants within intact mitochondria. In the present study, we provide evidence that aconitase is rapidly inactivated and subsequently reactivated when isolated cardiac mitochondria are treated with H(2)O(2). Reactivation of the enzyme is dependent on the presence of the enzyme's substrate, citrate. EPR spectroscopic analysis indicates that enzyme inactivation precedes release of the labile Fe-alpha from the enzyme's [4Fe-4S](2+) cluster. In addition, as judged by isoelectric focusing gel electrophoresis, the relative level of Fe-alpha release and cluster disassembly does not reflect the magnitude of enzyme inactivation. These observations suggest that some form of posttranslational modification of aconitase other than release of iron is responsible for enzyme inactivation. In support of this conclusion, H(2)O(2) does not exert its inhibitory effects by acting directly on the enzyme, rather inactivation appears to result from interaction(s) between aconitase and a mitochondrial membrane component responsive to H(2)O(2). Nevertheless, prolonged exposure of mitochondria to steady-state levels of H(2)O(2) or O(2)(-)(*) results in disassembly of the [4Fe-4S](2+) cluster, carbonylation, and protein degradation. Thus, depending on the pro-oxidant species, the level and duration of the oxidative stress, and the metabolic state of the mitochondria, aconitase may undergo reversible modulation in activity or progress to [4Fe-4S](2+) cluster disassembly and proteolytic degradation.

Authors+Show Affiliations

Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

14674759

Citation

Bulteau, Anne-Laure, et al. "Redox-dependent Modulation of Aconitase Activity in Intact Mitochondria." Biochemistry, vol. 42, no. 50, 2003, pp. 14846-55.
Bulteau AL, Ikeda-Saito M, Szweda LI. Redox-dependent modulation of aconitase activity in intact mitochondria. Biochemistry. 2003;42(50):14846-55.
Bulteau, A. L., Ikeda-Saito, M., & Szweda, L. I. (2003). Redox-dependent modulation of aconitase activity in intact mitochondria. Biochemistry, 42(50), 14846-55.
Bulteau AL, Ikeda-Saito M, Szweda LI. Redox-dependent Modulation of Aconitase Activity in Intact Mitochondria. Biochemistry. 2003 Dec 23;42(50):14846-55. PubMed PMID: 14674759.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Redox-dependent modulation of aconitase activity in intact mitochondria. AU - Bulteau,Anne-Laure, AU - Ikeda-Saito,Masao, AU - Szweda,Luke I, PY - 2003/12/17/pubmed PY - 2004/4/24/medline PY - 2003/12/17/entrez SP - 14846 EP - 55 JF - Biochemistry JO - Biochemistry VL - 42 IS - 50 N2 - It has previously been reported that exposure of purified mitochondrial or cytoplasmic aconitase to superoxide (O(2)(-)(*) or hydrogen peroxide (H(2)O(2)) leads to release of the Fe-alpha from the enzyme's [4Fe-4S](2+) cluster and to inactivation. Nevertheless, little is known regarding the response of aconitase to pro-oxidants within intact mitochondria. In the present study, we provide evidence that aconitase is rapidly inactivated and subsequently reactivated when isolated cardiac mitochondria are treated with H(2)O(2). Reactivation of the enzyme is dependent on the presence of the enzyme's substrate, citrate. EPR spectroscopic analysis indicates that enzyme inactivation precedes release of the labile Fe-alpha from the enzyme's [4Fe-4S](2+) cluster. In addition, as judged by isoelectric focusing gel electrophoresis, the relative level of Fe-alpha release and cluster disassembly does not reflect the magnitude of enzyme inactivation. These observations suggest that some form of posttranslational modification of aconitase other than release of iron is responsible for enzyme inactivation. In support of this conclusion, H(2)O(2) does not exert its inhibitory effects by acting directly on the enzyme, rather inactivation appears to result from interaction(s) between aconitase and a mitochondrial membrane component responsive to H(2)O(2). Nevertheless, prolonged exposure of mitochondria to steady-state levels of H(2)O(2) or O(2)(-)(*) results in disassembly of the [4Fe-4S](2+) cluster, carbonylation, and protein degradation. Thus, depending on the pro-oxidant species, the level and duration of the oxidative stress, and the metabolic state of the mitochondria, aconitase may undergo reversible modulation in activity or progress to [4Fe-4S](2+) cluster disassembly and proteolytic degradation. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/14674759/Redox_dependent_modulation_of_aconitase_activity_in_intact_mitochondria_ L2 - https://doi.org/10.1021/bi0353979 DB - PRIME DP - Unbound Medicine ER -