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The activation of adrenal cortex mitochondrial malic enzyme by Ca2+ and Mg2+.
- Source :
-
Biochemistry [Biochemistry] 1975 Jan 14; Vol. 14 (1), pp. 89-96. - Publication Year :
- 1975
-
Abstract
- Adrenal cortex mitochondria prepared by a standard method do not exhibit malic enzyme activity. Addition of physiological concentrations of Ca2+ and Mg2+ enables these mitochondria to reduce added NADP+ by malate to form free NADPH. Half-maximum activation of the mitochondrial malic enzyme requires 0.3 mM Ca2+ and 1 mM Mg2+. Solubilized mitochondrial malic enzymes is independent of Ca2+ and has a K M of 0.2 mM for Mg2+. The Ca2+ effect is dependent on an initial period of active Ca2+ uptake which also causes other changes in respiratory properties similar to those observed with mitochondria from other tissues. After Ca2+ accumulation has taken place, free Ca2+, but not additional accumulation, is still required for malic enzyme activity. The requirement for Mg2+ can be met by Mn2+ (1 mM). This concentration of Mn2+ alone yielded only a slight activation of mitochondrial malic enzyme while higher concentrations of Mn2+ alone gave good activation of the mitochondrial malic enzy.e The NADPH generated by the Ca2+-Mg2+ activated malic enzyme effectively supports the 11beta-hydroxylation of deoxycorticosterone, whereas in the presence of malate, or malate plus Mg2+ but absence of Ca2+, the energy linked transhydrogenase supplies all the required NADPH. The activated malic enzyme appears to be more efficient than transhydrogenase in generating NADPH to support 11beta-hydroxylation. Cyanide and azide have been found to inhibit solubilized mitochondrial malic enzyme.
Details
- Language :
- English
- ISSN :
- 0006-2960
- Volume :
- 14
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 1167337
- Full Text :
- https://doi.org/10.1021/bi00672a015