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PubMed1995

Role of reactive O2 in phagocyte-induced hypermetabolism and pulmonary injury.

Activated phagocytes possess an enormous capacity for O2 consumption via NADPH oxidase. NADPH oxidase partially reduces O2, forming superoxide (O2-). Host enzymes rapidly complete O2- reduction to H2O, leaving little trace of its prior existence. Our objectives were to estimate the magnitude of whole body phagocyte respiration and determine the contribution of NADPH-derived O2- to the ensuing phagocyte-induced pulmonary injury. These objectives were accomplished using specific inhibitors of NADPH oxidase, diphenyl iodonium (DPI) and di-2-thienyl iodonium (DTI). Guinea pigs received intravenous injections of DPI (3.5 mg/kg), DTI (7.5 mg/kg), or vehicle followed by phorbol myristate acetate (PMA). Phagocyte activation by PMA immediately increased whole body respiration from 13.6 to 16.1 ml O2.kg-1.min-1 (P < 0.05). DPI and DTI completely blocked the increase in respiration induced by PMA injection (P < 0.05). Baseline respiration was unchanged by the NADPH oxidase inhibitor alone. Likewise, there was no effect on the respiration of isolated heart and kidney mitochondria from animals receiving the inhibitor with or without PMA. DPI attenuated the pulmonary injury induced by PMA. DPI attenuated the pulmonary injury induced by PMA. The ratio of lung water weight to dry weight was lower (6.4 +/- 0.3 vs. 8.3 +/- 0.6) and arterial PO2 was higher (86 +/- 9 vs. 56 +/- 6 Torr) in animals receiving DPI plus PMA than in those receiving PMA alone. In conclusion, phagocyte activation in vivo increased total body respiration by approximately 18%. The burst in respiration is attributed to the phagocyte respiratory burst in which NADPH oxidase partially O2 to O2-.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Involvement of phenyl radicals in iodonium inhibition of flavoenzymes.

Iodonium inhibition of the flavoenzymes neutrophil NADPH oxidase and cytochrome P450 reductase has been suggested to require reductive metabolism of the inhibitor to a phenyl radical. Inhibition would ultimately result from covalent attachment of phenyl radicals to either the flavin cofactor or adjacent amino acid side chains important in catalysis. In this paper we provide evidence, using EPR techniques, that phenyl radicals are formed during reaction of iodonium diphenyl with reduced free flavin (FMN) and protein-bound (cytochrome P450 reductase or xanthine oxidase) flavin. Kinetic analysis indicated iodonium diphenyl to be an uncompetitive inhibitor of xanthine oxidase, suggesting the need for reduced enzyme for inhibition. A study of the catalytic and structural properties of different flavoenzymes suggested that only enzymes containing flavins that function in one-electron transfer are targets for iodonium inhibition.

Animals↗
PubMed1997

Inactivation and recovery of nitric oxide synthetic capability in cytokine-induced RAW 264.7 cells treated with "irreversible" NO synthase inhibitors.

As measured at 100 microM extracellular arginine, aminoguanidine produced a time- and concentration-dependent inactivation of nitric oxide (NO) synthesis by cytokine-induced RAW cells. Inactivation obeyed first-order kinetics and occurred at a maximal rate of 0.22 min(-1) with a half-maximal inactivation rate observed at a concentration of 670 microM aminoguanidine (K(I) value). Inactivation of NO synthetic activity in the presence of N(G)-methyl-L-arginine similarly followed first-order kinetics with a maximal inactivation rate of 0.07 min(-1) and a K(I) value of 170 microM. Inactivation of NO synthetic activity in the presence of diphenyliodonium chloride occurred with a maximal inactivation rate of 0.24 min(-1) with a K(I) value of 14 microM. Diphenyliodonium chloride also produced a first-order rate of inactivation of cytokine-inducible nitric oxide synthase (iNOS) activity affinity purified from cytokine-induced RAW cells with a maximal inactivation rate of its cytochrome c reductase activity of 0.24 min(-1) with a K(I) value of 18 microM. Cytokine-induced RAW cells were treated with aminoguanidine, N(G)-methyl-L-arginine, and diphenyliodonium chloride at concentrations and for a time sufficient to completely inactivate NO synthesis by the cells and were allowed to recover in drug-free medium. Despite the presence of cycloheximide, NO synthetic rate recovered from 70 to 90% of its pretreatment activity over 4 h in cells exposed to either aminoguanidine or N(G)-methyl-L-arginine but did not recover from exposure to diphenyliodonium chloride. Analysis by sucrose density gradient centrifugation of the cytochrome c reductase and citrulline-forming activities in extracts of cells recovered from aminoguanidine treatment revealed that recovery was accompanied by a diminished population of iNOS monomers with an increased population of iNOS dimers. This observation is consistent with the hypothesis that for the mechanism-based inactivator aminoguanidine, functional dimers can be assembled from "drug-undamaged" monomers during the recovery period.

Animals↗
PubMed2005

Activation of AP-1 through reactive oxygen species by angiotensin II in rat cardiomyocytes.

Cardiovascular pathogenesis induced by angiotensin II (Ang-II) is a complex process often connected to oxidative stress. In the present study we show that, 4 h after addition, Ang-II induces a four- to fivefold increase in AP-1 activity in cultured neonatal rat cardiomyocytes and that the intracellular level of reactive oxygen species (ROS) correlates with the extent of AP-1 binding activity. Ang-II stimulated ROS generation in rat cardiomyocytes in a dose- and time-dependent manner. These effects of Ang-II were suppressed by the Ang-II receptor type I (AT1) inhibitor CV-11974 as well as by the antioxidants diphenylene iodonium (DPI) and N-acetyl-L-cysteine (NAC), but not by AT2 antagonist PD 122319. Furthermore, Ang-II induced a two- to threefold increase in protein synthesis and cell size during 12-24 h, which could be inhibited by CV-11974 as well as by DPI and NAC. Because the rat cardiomyocytes strongly expressed gp91(phox), this suggests that ROS generated in a gp91-containing NADPH oxidase are involved in signal transduction leading to AP-1 activation. Together, these findings indicate that Ang-II elicits the activation of the redox-sensitive AP-1 via ROS through AT1, resulting in effects on cardiomyocyte function such as hypertrophy.

Acetylcysteine↗
PubMed1997

Modulation by both diphenyliodonium and diphenyleneiodonium of [3H]MK-801 binding to rat brain synaptic membranes.

Binding of [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne (MK-801) was significantly inhibited by the addition of several different compounds related to generation of nitric oxide (NO) at 100 microM in rat brain synaptic membranes. These included sodium nitroprusside, diphenyliodonium (DI), diphenyleneiodonium (DPI) and methylene blue. However, neither S-nitroso-N-acetylpenicillamine nor S-nitroso-L-glutathione inhibited binding at 100 microM. Both DI and DPI inhibited binding in a concentration-dependent manner at a concentration range of over 1 microM, while further addition of spermidine (SPD) significantly attenuated the potency of DPI to inhibit binding without affecting that of DI. In contrast, SPD induced significant potentiation of the ability of unlabelled MK-801 to displace [3H]MK-801 binding in a fashion sensitive to antagonism by the novel polyamine antagonist bis-(3-aminopropyl)nonanediamine. This novel polyamine antagonist also prevented the reversing effect of SPD on inhibition by DPI of [3H]MK-801 binding. Moreover, DPI competitively exacerbated the ability of SPD to potentiate [3H]MK-801 binding in the presence of both L-glutamic acid and glycine at maximally effective concentrations. On the other hand, SPD was effective in reversing the inhibition by DPI in cerebellar, but not hippocampal, synaptic membranes. These results suggest that both DI and DPI may modulate synaptic responses mediated by the N-methyl-D-aspartate receptor through inhibition of opening processes of the ion channel in a manner irrespective of generation of NO radicals in particular situations. Possible involvement of the polyamine domain in the inhibition by DPI is also suggested.

Animals↗
PubMed1999

Potential role of a membrane-bound NADH oxidoreductase in nitric oxide release and arterial relaxation to nitroprusside.

The site of metabolism in vascular smooth muscle responsible for the release of nitric oxide (NO) from nitroprusside is not well established. In this study we observed that a membrane-bound NADH oxidoreductase in the pulmonary artery activates nitroprusside to release NO, and we examined whether this process could potentially participate in relaxation to nitroprusside. Relaxation to nitroprusside in bovine calf pulmonary artery is inhibited by a scavenger of NO and by an antagonist of NO stimulation of guanylate cyclase. A flavoprotein probe that inhibits pulmonary artery NADH oxidoreductase (1 micromol/L diphenyliodonium) and electron acceptors for NADH oxidoreductase (0.3 mmol/L nitroblue tetrazolium and 0.1 mmol/L ferricyanide) inhibited pulmonary artery relaxation to nitroprusside, but not to nitroglycerin. Pulmonary arteries were observed to promote the release of NO from nitroprusside in vitro, and NO release was inhibited by the presence of nitroblue tetrazolium, ferricyanide, and diphenyliodonium. In homogenates of pulmonary arteries, NADH (0.1 mmol/L) increased the release of NO from nitroprusside by approximately 6-fold, whereas NADPH, mitochondrial substrates, and other redox cofactors had minimal effects on NO release, and the action of NADH on nitroprusside was inhibited by nitroblue tetrazolium, ferricyanide, and diphenyliodonium. A membrane fraction enriched in NADH oxidoreductase activity showed a NADH-dependent release of NO from nitroprusside; nitroprusside caused NADH consumption, and it also inhibited the NADH-dependent reduction of nitroblue tetrazolium. Thus, a membrane-bound NADH oxidoreductase appears to contribute to the release of NO from nitroprusside, but not nitroglycerin, in calf pulmonary artery.

Animals↗
PubMed2002

Alpha-tocopherol decreases superoxide anion release in human monocytes under hyperglycemic conditions via inhibition of protein kinase C-alpha.

Diabetes is a major risk factor for premature atherosclerosis, and oxidative stress appears to be an important mechanism. Previously, we showed that diabetic monocytes produce increased superoxide anion (O(2)(-)), and alpha-tocopherol (AT) supplementation decreases this. The aim of this study was to elucidate the mechanism(s) of O(2)(-) release and inhibition by AT under hyperglycemic (HG) conditions in monocytes. O(2)(-) release, protein kinase C (PKC) activity, and translocation of PKC-alpha and -betaII and p47phox were increased in THP-1 cells (human monocytic cell line) under HG (15 mmol/l glucose) conditions, whereas AT supplementation inhibited these changes. AT, NADPH oxidase inhibitors (apocynin and diphenyleneiodonium chloride [DPI]), and an inhibitor to PKC-alpha and other isoforms (2,2',3,3',4,4'-hexahydroxy-1,1'-biphenyl-6,6'-dimethanol dimethyl ether [HBDDE]) but not PKC-beta II (LY379196) decreased O(2)(-) release and p47phox translocation. Antisense oligodeoxynucleotides to PKC-alpha and p47phox but not to PKC-betaII inhibited HG-induced O(2)(-) release and p47phox translocation in THP-1 cells. Under HG conditions, reactive oxygen species release from monocytes was not inhibited by agents affecting mitochondrial metabolism but was inhibited in human endothelial cells. We conclude that under HG conditions, monocytic O(2)(-) release is dependent on NADPH oxidase activity but not the mitochondrial respiratory chain; HG-induced O(2)(-) release is triggered by PKC-alpha, and AT inhibits O(2)(-) release via inhibition of PKC-alpha.

Acetophenones↗
PubMed2004

Reactive oxygen species mediate chloroquine-induced expression of chemokines by human astroglial cells.

We have previously demonstrated that chloroquine may evoke inflammatory responses in the central nervous system by inducing expression of pro-inflammatory cytokines by astroglial cells. In this study, we further examined the molecular mechanism responsible for chloroquine-induced activation of NF-kappaB and subsequent expression of chemokines by astroglial cells. We observed that (1) chloroquine induced expression of chemokines such as CCL2 and CXCL8 in a dose- and time-dependent manner in human astroglial cells; (2) other lysosomotropic agents such as ammonium chloride and bafilomycin A1 had minimal effects on chemokine expression; (3) inhibition of NF-kappaB by MG-132 and TPCK suppressed chloroquine-induced mRNA expression of chemokines; (4) chloroquine increased the intracellular level of reactive oxygen species (ROS) in a dose- and time-dependent manner by human astroglial cells, but not by monocytic/microglial cells; (5) chloroquine-induced increase of intracellular ROS level was suppressed by pre-incubation with diphenyl iodonium (DPI) and N-acetyl cysteine (NAC); and (6) inhibition of chloroquine-induced ROS production by DPI or NAC suppressed chloroquine-mediated activation of NF-kappaB and subsequent mRNA expression of chemokines in astroglial cells. These results collectively suggest that chloroquine generates ROS, which is responsible for NF-kappaB activation and subsequent expression of pro-inflammatory chemokines in human astroglial cells.

Acetylcysteine↗
PubMed1991

Diphenylene iodonium, an inhibitor of free radical formation, inhibits platelet aggregation.

Diphenylene iodonium is an inhibitor of the enzyme NADPH-oxidase and prevents the generation of oxygen-derived free radicals in neutrophils (Cross and Jones, 1986). Here we show that diphenylene iodonium (0.25-2 microM) inhibited, according to the dose, thrombin-induced platelet-aggregation in human washed platelets and ADP-induced platelet aggregation in platelet-rich plasma. At the concentrations which inhibited platelet aggregation diphenylene iodonium did not alter platelet concentrations of cAMP or cGMP but enhanced the anti-platelet activity of iloprost, sodium nitroprusside or cultured endothelial cells. These findings highlight the importance of free radicals as platelet pro-aggregatory agents.

Adenosine Diphosphate↗
PubMed2005

Acrosome reaction in bovine spermatozoa: role of reactive oxygen species and lactate dehydrogenase C4.

After capacitation, mammalian spermatozoa accomplish the acrosome reaction (AR), a well-controlled exocytosis process crucial to fertilize mature oocytes that involves several protein kinases such as protein kinase A (PKA), C (PKC), and tyrosine kinase (PTK). Reactive oxygen species (ROS) are involved in both bovine sperm capacitation and AR. Lactate dehydrogenase C4 (LDH-C4) was associated with bovine and mouse sperm capacitation. Our aims were to study the participation of LDH-C4 to contribute with the status redox required for AR and the role of ROS in the regulation of PKA, PKC, and PTK involved in the exocytotic event. Sodium oxamate, an inhibitor of LDH-C4, prevented the AR induced by lysophosphatidylcholine (LPC) or NADH. Hydrogen peroxide promoted and superoxide dismutase (scavenger of superoxide), catalase (scavenger of hydrogen peroxide), diphenyleneiodinum, diphenyliodonium, cibacron blue, and lapachol (inhibitors of NADPH oxidase) prevented the AR, suggesting that ROS and a sperm oxidase are involved in the AR induced by these compounds. Inhibitors of PKA, PKC, and PTK also prevented the AR induced by LPC or NADH, suggesting the involvement of these kinases in the process. These results suggest that LDH-C4 may participate in the regulation of the redox status required to achieve the AR in bovine spermatozoa and that ROS are key elements in the regulation of protein kinases associated with the AR process.

Acrosome↗
PubMed1991

Inhibition of O2-. generating oxidase of neutrophils by iodonium biphenyl in a cell free system: effect of the redox state of the oxidase complex.

The conditions of inhibition of neutrophil O2-. generating oxidase by iodonium biphenyl (IBP) were studied. In a cell free system of oxidase activation consisting of neutrophil membranes and cytosol, GTP-gamma-S, Mg2+ and arachidonic acid, the inhibitory effect of IBP depended on the redox conditions of the medium. Inhibition was observed when the medium was supplemented with dithionite or NADPH. When the cell free system was incubated with IBP in the absence of reducing agents, full oxidase activity was recovered after removal of free IBP by gel filtration. Bovine neutrophil membranes, but not cytosol, contained component(s) sensitive to IBP. Upon treatment of neutrophil membranes by IBP followed by reduction, the spectrum of reduced cytochrome b558 was modified, suggesting that cytochrome b558 is a target site for IBP.

Animals↗
PubMed2001

Evidence for simultaneous binding of dissimilar substrates by the Escherichia coli multidrug transporter MdfA.

The mechanism by which multidrug transporters interact with structurally unrelated substrates remains enigmatic. Based on transport competition experiments, photoaffinity labeling, and effects on enzymatic activities, it was proposed in the past that multidrug transporters can interact simultaneously with a number of dissimilar substrate molecules. To study this phenomenon, we applied a direct binding approach and transport assays using the Escherichia coli multidrug transporter MdfA, which exports both positively charged (e.g., tetraphenylphosphonium, TPP(+)), zwitterionic (e.g., ciprofloxacin), and neutral (e.g., chloramphenicol) drugs. The interaction of MdfA with various substrates was examined by direct binding assays with the purified transporter. The immobilized MdfA binds TPP(+) in a specific manner, and all the tested positively charged substrates inhibit TPP(+) binding. Surprisingly, although TPP(+) binding is not affected by zwitterionic substrates, the neutral substrate chloramphenicol stimulates TPP(+) binding by enhancing its affinity to MdfA. In contrast, transport competition assays show inhibition of TPP(+) transport by chloramphenicol. We suggest that MdfA binds TPP(+) and chloramphenicol simultaneously to distinct but interacting binding sites, and the interaction between these two substrates during transport is discussed.

Bacterial Proteins↗
PubMed1998

Interaction of alpha-phenyl-N-tert-butyl nitrone and alternative electron acceptors with complex I indicates a substrate reduction site upstream from the rotenone binding site.

Mitochondrial complexes I, II, and III were studied in isolated brain mitochondrial preparations with the goal of determining their relative abilities to reduce O2 to hydrogen peroxide (H2O2) or to reduce the alternative electron acceptors nitroblue tetrazolium (NBT) and diphenyliodonium (DPI). Complex I and II stimulation caused H2O2 formation and reduced NBT and DPI as indicated by dichlorodihydrofluorescein oxidation, nitroformazan precipitation, and DPI-mediated enzyme inactivation. The O2 consumption rate was more rapid under complex II (succinate) stimulation than under complex I (NADH) stimulation. In contrast, H2O2 generation and NBT and DPI reduction kinetics were favored by NADH addition but were virtually unobservable during succinate-linked respiration. NADH oxidation was strongly suppressed by rotenone, but NADH-coupled H2O2 flux was accelerated by rotenone. Alpha-phenyl-N-tert-butyl nitrone (PBN), a compound documented to inhibit oxidative stress in models of stroke, sepsis, and parkinsonism, partially inhibited complex I-stimulated H2O2 flux and NBT reduction and also protected complex I from DPI-mediated inactivation while trapping the phenyl radical product of DPI reduction. The results suggest that complex I may be the principal source of brain mitochondrial H2O2 synthesis, possessing an "electron leak" site upstream from the rotenone binding site (i.e., on the NADH side of the enzyme). The inhibition of H2O2 production by PBN suggests a novel explanation for the broad-spectrum antioxidant and antiinflammatory activity of this nitrone spin trap.

Animals↗
PubMed2000

Endogenous nitric oxide is implicated in the regulation of lipolysis through antioxidant-related effect.

We studied the influence of nitric oxide (NO) endogenously produced by adipocytes in lipolysis regulation. Diphenyliodonium (DPI), a nitric oxide synthase (NOS) inhibitor, was found to completely suppress NO synthesis in intact adipocytes and was thus used in lipolysis experiments. DPI was found to decrease both basal and dibutyryl cAMP (DBcAMP)-stimulated lipolysis. Inhibition of DBcAMP-stimulated lipolysis by DPI was prevented by S-nitroso-N-acetyl-penicillamine (SNAP), a NO donor. This antilipolytic effect of DPI was also prevented by two antioxidants, ascorbate or diethyldithiocarbamic acid (DDC). Preincubation of isolated adipocytes with DPI (30 min) before exposure to DBcAMP almost completely abolished the stimulated lipolysis. Addition of SNAP or antioxidant during DPI preincubation restored the lipolytic response to DBcAMP, whereas no preventive effects were observed when these compounds were added simultaneously to DBcAMP. Exposure of isolated adipocytes to an extracellular generating system of oxygen species (xanthine/xanthine oxidase) or to H(2)O(2) also resulted in an inhibition of the lipolytic response to DBcAMP. H(2)O(2) or DPI decreased cAMP-dependent protein kinase (PKA) activation. The DPI effect on PKA activity was prevented by SNAP, ascorbate, or DDC. These results provide clear evidence that 1) the DPI antilipolytic effect is related to adipocyte NOS inhibition leading to PKA alterations, and 2) endogenous NO is required for the cAMP lipolytic process through antioxidant-related effect.

Adipocytes↗
PubMed1999

Overexpression of the FAD-binding domain of the sulphite reductase flavoprotein component from Escherichia coli and its inhibition by iodonium diphenyl chloride.

SiR-FP43, the NADPH- and FAD-binding domain of the Escherichia coli sulphite reductase flavoprotein component (SiR-FP), has been overexpressed and characterized. It folds independently, retaining FAD as a cofactor and the catalytic properties associated with the presence of this cofactor. Iodonium diphenyl chloride (IDP) was shown to be a very efficient inhibitor of SiR-FP43 and SiR-FP60, the monomeric form of SiR-FP, containing both FMN and FAD as cofactors (K(i) = 18.5 +/- 5 microM, maximal inactivation rate = 0.053 +/- 0.005 s(-1)). In both cases, inactivation was shown to result from covalent binding of a phenyl group to FAD exclusively, in marked contrast with previous results obtained with cytochrome P450 reductase (CPR), where FMN and a tryptophan were phenylated, but not FAD. However, our kinetic analyses are in agreement with the inhibition mechanism demonstrated with CPR [Tew (1993) Biochemistry 32, 10209-10215]. Nine different FAD phenylated adducts were isolated and, for the first time, two FAD phenylated adducts were identified directly after extraction from a protein. Taken together, our results have shown that flavoprotein inactivation by IDP is not a reliable indicator for a flavin radical intermediate in catalysis.

Base Sequence↗
PubMed1998

Generation of reactive oxygen species in a human keratinocyte cell line: role of calcium.

In the human keratinocyte cell line HaCaT, reactive oxygen species (ROS) were generated in a dose- and time-dependent manner in response to epidermal growth factor (EGF), bradykinin, thapsigargin, and the Ca(2+)-ionophore A23187, agonists that interact with different primary cell targets. ROS formation was assessed by both chemiluminescence- and fluorescence-based methods. The ROS evoked by EGF and bradykinin decayed within 8 and 4 min, respectively, this transient effect resulting probably from down-regulation of the specific agonist receptors or dissipation of the secondary signals. In contrast, the response to thapsigargin and A23187 was sustained for at least 15 min. Extracellular Ca2+ and a rise in intracellular Ca2+ concentration ([Ca2+]i) proved essential for ROS production. Chelation by BAPTA suppressed ROS formation. Direct measurement of [Ca2+]i using fura fluorescence revealed that EGF and bradykinin evoked a modest, transient [Ca2+]i elevation of less than twofold, whereas with thapsigargin and A23187 there was a sustained two- to fourfold elevation. For each agonist, the kinetics of the rise and decay of [Ca2+]i were similar to those of ROS. The enzyme(s) involved in ROS formation were inhibited by diphenyleneiodonium, indicating dependence on FAD. Our results suggest a close link between ROS and changes in [Ca2+]i generated by growth factors and hormones. This is a particularly interesting connection because elevation of ROS and/ or [Ca2+]i has been linked to cell proliferation, differentiation, and apoptosis.

Biphenyl Compounds↗
PubMed1995

Using lipoate enantiomers and thioredoxin to study the mechanism of the 2-oxoacid-dependent dihydrolipoate production by the 2-oxoacid dehydrogenase complexes.

The thioredoxin-catalyzed insulin reduction by dihydrolipoate was applied to study the 2-oxoacid: lipoate oxidoreductase activity of 2-oxoacid dehydrogenase complexes. The enzymatic and non-enzymatic mechanisms of the transfer of reducing equivalents from the complexes to free lipoic acid (alpha-lipoic acid, 6,8-thiooctic acid) were distinguished using the high stereoselectivity of the complex enzymes to the R-enantiomer of lipoate. Unlike these enzymes, thioredoxin from E. coli exhibited no stereoselectivity upon reduction with chemically obtained dihydrolipoate. However, coupled to the dihydrolipoate production by the dehydrogenase complexes, the process was essentially sensitive both to the enantiomer used and the dihydrolipoyl dehydrogenase activity of the complexes. These results indicated the involvement of the third complex component, dihydrolipoyl dehydrogenase, in the 2-oxoacid-dependent dihydrolipoate formation. The implication of the investigated reaction for a connection between thioredoxin and the 2-oxoacid dehydrogenase complexes in the mitochondrial metabolism are discussed.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗