Action of Magnesium Ion on Diphosphopyridine Nucleotide-linked Isocitrate Dehydrogenase from Bovine Heart

Plaut, G.W.E.; Schramm, Vern L.; Aogaichi, Tadashi

doi:10.1016/s0021-9258(19)42864-0

Cited by 51 publications

(17 citation statements)

References 21 publications

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“…However, the constants are not comparable between experiments where incubation conditions varied. Magnesium isocitratehas been reported to be the actual substrate of the DPN-linked enzyme and the values of So.5 calculated for magnesium DL-isocitrate shown in parentheses of Table I are in agreement with those reported previously (Plaut et al, 1974). By analogy it is likely that the divalent metal ion chelates of garcinia acid or homoisocitrate are the substrates of the enzyme, and presentation of constants based on chelate concentrations would be desirable.…”

Section: Resultssupporting

confidence: 86%

“…Thus, the apparent large discrepancies in constants for total DL-garcinia acid shown in Table I and in experiment 1 of Table II are due to variations in the ratios of magnesium to garcinia acid as well as differences in pH and ADP concentration. In Table I a high ratio of isocitrate analog to magnesium concentration was maintained to hold most of the magnesium in the chelate form and to minimize the inhibitory effect of free Mg2+ (Plaut et al, 1974). In experiment 2 of Table II, total magnesium was held constant and was in excess (6.6 mM) of the variable concentrations of garcinia acids (0.16-1.6 mM) used; in experiment 1 (Table II) the concentration of substrate was varied at a constant ratio of [total garcinia acid]/[total MnSQ4] = 10.…”

Section: Resultsmentioning

confidence: 99%

“…This and the observation that stoichiometric amounts of DPNH and of the a-keto acid are formed from homoisocitrate (Table V) indicate that the reaction catalyzed by the DPN-linked isocitrate dehydrogenase is homoisocitrate + DPN+ --ketoadipate + CO2 + DPNH + H+ The Effect of ADP on the Oxidation of Analogs by DPN-Linked Isocitrate Dehydrogenase. ADP is a positive modifier for the enzyme from a number of animal tissues leading to a lowering of the apparent Km of total isocitrate (Chen and Plaut, 1963b) or of magnesium isocitrate-the actual substrate of the enzyme-and a lowering of the Hill coefficient from = 2 to = 1 (Plaut et al, 1974). When inactive, i.e., less than 0.5% of the activity observed with optimal concentrations of isocitrate.…”

Section: Resultsmentioning

confidence: 99%

“…Nucleotides, Tris, and Hepes2 were purchased from Sigma, inorganic chemicals of reagent grade from Mallinckrodt, and organic chemicals from Aldrich. The cation exchange resins AG 50W-X12 (200-400 mesh) and Bio-Rex 70 (200-400 mesh) were from Bio-Rad. DL-threo-Isocitric lactone from Sigma was recrystallized from ethyl butyrate (Plaut et al, 1974).…”

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confidence: 99%

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Substrate activity of structural analogs of isocitrate for isocitrate dehydrogenases from bovine heart

Plaut¹,

Beach²,

Aogaichi³

1975

Biochemistry

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D-Garcinia acid (D-threo-1,2-dihydroxy-1,2,3-propanetricarboxylate), like D-isocitrate, has an alpha-DS-hydroxyl group and a beta-LS configuration of the second carboxyl group. The maximal velocity of pyridine nucleotide reduction with D-garcinia acid is 8 and 21% of D-threo-isocitrate with the DPN-linked and TPN-linked isocitrate dehydrogenase from bovine heart, respectively. The other stereoisomers of hydroxycitrate [L-garcinia acid, D- and L-hibiscus acid (D- and L-erythro-1,2-dihydroxy-1,2,3-propanetricarboxylate)] are inactive. DL-threo-Homoisocitrate (DL-threo-1-hydroxy-1,2,4-butanetricarboxylate) supports DPN+ reduction at 10-15% of the rate observed for isocitrate with the DPN-specific enzyme, but is not a substrate for TPN-linked isocitrate dehydrogenase. The values of apparent S0.5 for total isocitrate and total garcinia acid are similar with both enzymes; the apparent S0.5 of total homoisocitrate is two- to threefold higher than that of total isocitrate with the DPN-linked enzyme. Enzymatic oxidative decarboxylation of garcinia acid and homoisocitrate leads to formation of alpha-keto-beta-hydroxyglutarate and alpha-ketoadipate, respectively. DL-Methylmalate (DL-1-hydroxy-2-methylsuccinate) is inactive as a substrate for either dehydrogenase as are the newly synthesized compounds: DL-threo-gamma-isocitrate amide (DL-threo-1-hydroxy-3-carbamy01,2-propanedicarboxylate), beta-methyl-DL-isocitrate (DL-1-hydroxy-2-methyl-1,2,3-propanetricarboxylate), beta-methyl-DL-garcinia acid (DL-threo-1-hydroxyl-2-methoxy-1,2,3-propanetricarboxylate), DL-1-hydroxyl-1,2,2-ethanetricarboxylate, and DL-1,4-dihydroxy-1,2-butanedicarboxylate.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Substrate activity of structural analogs of isocitrate for isocitrate dehydrogenases from bovine heart

Plaut¹,

Beach²,

Aogaichi³

1975

Biochemistry

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“…*" was the allosteric activator of purified NADisocitrate dehydrogenase from ox heart (Plaut et al, 1974) and porcine heart (Ehrlich & Colman, 1981). At an S05(app) for ADP3" of about 0.24 mM (Gabriel & Plaut, 1984), the intramitochondrial free ADP concentrations (Table III) appear to be adequate for activation and, possibly, regulation of the activity of the enzyme during state 4 to state 3 transitions.…”

Section: Free Adp3mentioning

confidence: 99%

Inhibition of bovine heart NAD-specific isocitrate dehydrogenase by reduced pyridine nucleotides: modulation of inhibition by ADP, NAD+, calcium(2+), citrate, and isocitrate

Gabriel¹,

Plaut²

1984

Biochemistry

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The activity of NAD-dependent isocitrate dehydrogenase from bovine heart was inhibited by NADH (apparent Ki about 4.3 microM) and NADPH (Ki about 9.8 microM) at subsaturating substrate concentrations at pH 7.4. The inhibition by NADH or NADPH was reversed competitively by magnesium isocitrate in the presence of ADP, but not without ADP. Reversal of inhibition by NADH or NADPH with respect to NAD+ was competitive or of the linear mixed type depending on whether ADP was absent or present. ADP3- (0.2 mM) increased the Ki(app) for NADPH from 9.8 to 27.1 microM; further addition of Ca2+ (0.2 mM) raised the Ki(app) to 127 microM. For the modification of NADPH inhibition by ADP, S0.5 for Ca2+ was approximately 48 microM. This compares to the Km for Ca2+ of 0.3-1 microM for the activation of the enzyme without NADPH [Denton, R. M., Richards, D. A., & Chin, J. G. (1978) Biochem. J. 176, 899-906; Aogaichi, T., Evans, J., Gabriel, J., & Plaut, G. W. E. (1980) Arch. Biochem. Biophys. 204, 350-360]. ADP did not affect the Ki for NADH. Magnesium citrate, which was about 100-fold more effective as a positive modifier of the enzyme with ADP than without ADP [Gabriel, J. L., & Plaut, G. W. E. (1983) Fed. Proc., Fed. Am. Soc. Exp. Biol. 42, 2082], reversed competitively the inhibition by NADPH in the presence of ADP, but not without ADP. Magnesium citrate did not reverse NADH inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

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Towards the molecular basis for the regulation of mitochondrial dehydrogenases by calcium ions

Nichols¹,

Denton²

1995

Signal Transduction Mechanisms

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Action of Magnesium Ion on Diphosphopyridine Nucleotide-linked Isocitrate Dehydrogenase from Bovine Heart

Cited by 51 publications

References 21 publications

Substrate activity of structural analogs of isocitrate for isocitrate dehydrogenases from bovine heart

Substrate activity of structural analogs of isocitrate for isocitrate dehydrogenases from bovine heart

Inhibition of bovine heart NAD-specific isocitrate dehydrogenase by reduced pyridine nucleotides: modulation of inhibition by ADP, NAD+, calcium(2+), citrate, and isocitrate

Towards the molecular basis for the regulation of mitochondrial dehydrogenases by calcium ions

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