Location of the Coenzyme Binding Site in the Porcine Mitochondrial NADP-dependent Isocitrate Dehydrogenase

The Mitochondrial Calcium Uniporter Matches Energetic Supply with Cardiac Workload during Stress and Modulates Permeability Transition

“…This was a somewhat surprising since we thought NADPH generation was primarily extra-mitochondrial via the pentose phosphate pathway. However, mitochondrial enzymes such as malic enzyme, NADP-linked isocitrate dehydrogenase and mitochondrial methylenetetrahydrofolate dehydrogenase are other significant sources of NADPH production (Fan et al, 2014; Huang and Colman, 2005; Palmieri et al, 2015; Yang et al, 1996). It’s intriguing to think that this may be another metabolic consequence of altering the m Ca 2+ microdomain during stress, be it direct or indirect modulation.…”

Structural and Functional Properties of Isocitrate Dehydrogenase from the Psychrophilic Bacterium Desulfotalea psychrophila Reveal a Cold-active Enzyme with an Unusual High Thermal Stability

“…The high K m for isocitrate in DpIDH suggests a lower affinity than that in DhIDH and TmIDH, in the whole temperature range of the characterization ( Figure 2(c)). At 25°C, K m for isocitrate in DpIDH is 15-fold higher than that for PcIDH (8.37 μM), 43 and is drastically affected by temperature elevation. Even a temperatures as low as 25°C, the K m -value appears to be outside the physiological range and at 45°C it is in the millimolar range.…”

“…46,47 In addition, Arg83 and Thr311 (Arg81 and Thr307 in DpDIH) have been found close to the nicotinamide ribose and 5′-phosphate, and Asn328 (Asn324 in DpIDH) is adjacent to the adenine ring in PcIDH. 43 All of the above-mentioned amino acid residues are conserved, and have similar orientation and conformation in the compared enzymes, underlining their important function in binding and catalysis, and displaying a high level of structural similarity encountered within subfamily II.…”

“…A lower catalytic activity at low temperatures than for mesophilic homologues has been reported for a few other enzyme families, such as GTPase and chitanase. 41,42 At 25°C PcIDH is reported to have a specific activity of 42.9 units/mg, 43 corresponding to a calculated k cat of 33.3 s − 1 . DpIDH has a k cat of 35.6 s − 1 at 25°C, thus showing a catalytic activity highly similar to that of PcIDH at this temperature but significantly lower than that of DhIDH (Figure 2 (a)).…”

The Role of Mitochondrial NADPH-Dependent Isocitrate Dehydrogenase in Cancer Cells

“…The NADP + binding site was originally predicted from the E. coli IDH structures, positioning the 2-hydroxyl-bound phosphate to interact with His315 and Lys374 of porcine IDH2 [50]. Porcine Arg83 enhances NADP + affinity by hydrogen bonding with the 3′-OH of the nicotinamide ribose, and Asn328 provides a hydrogen bond to the N1 of adenine [53]. For efficient coenzyme site function, a hydroxyl group must be present at position 373 (Thr373 of the porcine sequence), whereas Asp375 and Lys260 contribute to coenzyme affinity and catalysis [54, 55].…”