FIGURE 6.

pH dependence of l-2-HG dehydrogenase (l-2-HGDH). The l-2-HGDH activity of isolated permeabilized mouse heart mitochondria was measured spectrophotometrically using either an iodonitrotetrazolium (INT) to formazan coupled assay (A) or by direct LC-MS/MS assay of α-KG formation (B). A, formazan production at various pH values for mitochondria supplied with 500 μm l-2-HG. B, α-KG production at various pH values for mitochondria supplied with 500 μm l-2-HG. The data are means ± S.E., n = 4. *, p < 0.05 (two-way ANOVA followed by Student's t test) compared with corresponding value at pH 7.4.