Calcium ions and the regulation of NAD+-linked isocitrate dehydrogenase from the mitochondria of rat heart and other tissues
- 15 December 1978
- journal article
- research article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 176 (3), 899-906
- https://doi.org/10.1042/bj1760899
Abstract
The effects of Ca2+ on the activity of isocitrate dehydrogenase (NAD+) in extracts of rat heart mitochondria were explored in the presence of MgCl2 by using EGTA buffers. In the absence of ADP, Ca2+ (about 30 micrometer) resulted in a slight increase in apparent Km for threo-Ds-isocitrate; in the presence of ADP, Ca2+ (about 25 micrometer) greatly lowered the apparent Km for threo-Ds-isocitrate from 227 micrometer to 53 micrometer without changing the maximum velocity. At 100 micrometer-threo-Ds-isocitrate and 1 mM-ADP, there was an 8-fold activation by Ca2+, with a Km for Ca2+ of 1.2 micrometer. This activation was also observed with Sr2+ (Km 3.1 micrometer), but not with Mn2+ (at concentrations below 2.5 micrometer). Similar effects of Ca2+ were also observed on isocitrate dehydrogenase (NAD+) activity in extracts of mitochondria from liver, kidney, brown adipose tissue and white adipose tissue of the rat. The possible regulatory role of changes in the intramitochondrial concentration of Ca2+ is discussed.This publication has 31 references indexed in Scilit:
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