Regulation by Magnesium of Potato Tuber Mitochondrial Respiratory Activities |
| |
Authors: | Joaquim?A.?F.?Vicente author-information" > author-information__contact u-icon-before" > mailto:jvicente@ci.uc.pt" title=" jvicente@ci.uc.pt" itemprop=" email" data-track=" click" data-track-action=" Email author" data-track-label=" " >Email author,Vítor?M.?C.?Madeira,Anibal?E.?Vercesi |
| |
Affiliation: | (1) Departamento de Botânica, Universidade de Coimbra, Coimbra, Portugal;(2) Departamento de Bioquímica da Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Coimbra, Portugal;(3) Departamento de Patologia Clínica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brasil;(4) Departamento de Zoologia, FCT, Universidade de Coimbra, 3004-517 Coimbra, Portugal |
| |
Abstract: | Dehydrogenase activities of potato tuber mitochondria and corresponding phosphorylation rates were measured for the dependence on external and mitochondrial matrix Mg2+. Magnesium stimulated state 3 and state 4 respiration, with significantly different concentrations of matrix Mg2+ required for optimal activities of the several substrates. Maximal stimulation of respiration with all substrates was obtained at 2-mM external Mg2+. However, respiration of malate, citrate, and -ketoglutarate requires at least 4-mM Mg2+ inside mitochondria for maximization of dehydrogenase activities. The phosphorylation system, requires a low level of internal Mg2+ (0.25 mM) to reach high activity, as judged by succinate-dependent respiration. However, mitochondria respiring on citrate or -ketoglutarate only sustain high levels of phosphorylation with at least 4-mM matrix Mg2+. Respiration of succinate is active without external and matrix Mg2+, although stimulated by the cation. Respiration of -ketoglutarate was strictly dependent on external Mg2+ required for substrate transport into mitochondria, and internal Mg2+ is required for dehydrogenase activity. Respiration of citrate and malate also depend on internal Mg2+ but, unlike -ketoglutarate, some activity still remains without external Mg2+. All the substrates revealed insensitive to external and internal mitochondrial Ca2+, except the exogenous NADH dehydrogenase, which requires either external Ca2+ or Mg2+ for detectable activity. Calcium is more efficient than Mg2+, both having cumulative stimulation. Unlike Ca2+, Mn2+ could substitute for Mg2+, before and after addition of A23, showing its ability to regulate phosphorylation and succinate dehydrogenase activities, with almost the same efficiency as Mg2+. |
| |
Keywords: | Magnesium regulation plant mitochondria mitochondrial respiration A23187 mitochondrial Mg2+ depletion |
本文献已被 PubMed SpringerLink 等数据库收录! |
|