Bacterial and mammalian thioredoxin systems activate iodothyronine 5′-deiodination

Das, Arun K.; Hummel, Brian C. W.; Gleason, Florence K.; Holmgren, Arne; Walfish, Paul G.

doi:10.1139/o88-057

Cited by 10 publications

(6 citation statements)

References 19 publications

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“…Substitution experiments [25] showed that Escherichia coli thioredoxin could replace Fraction B. Highly purified thioredoxin reductase and thioredoxin of rat liver cytosol, together with NADPH, were shown by others to support 5'-deiodination of rT3 [25]. These various findings strongly suggested that the stimulatory activity that we reported in rat liver [7-9] could be attributed to the thioredoxin system.…”

Section: Discussionmentioning

confidence: 51%

“…Our previously reported investigations of the 5'-DI cofactor system of rat liver cytosol utilized partially purified chromatographic Fractions A and B, together with NADPH [7][8][9]25], and indicated that this system resembled the thioredoxin system in the following respects: (a) NADPH-dependence, (b) requirement for a reductase of Mr > 60000 plus a dithiol of Mr approx. 13000 and pl < 6, (c) sensitivity to arsenite and iodoacetamide, (d) resistance to thermal inactivation, (e) enhancement by DTT and (f) inhibition of 5'-DIsupportive activity of Fractions A and B by anti-(thioredoxin reductase) IgG and by anti-thioredoxin IgG respectively.…”

Section: Discussionmentioning

confidence: 97%

“…13000 and pl < 6, (c) sensitivity to arsenite and iodoacetamide, (d) resistance to thermal inactivation, (e) enhancement by DTT and (f) inhibition of 5'-DIsupportive activity of Fractions A and B by anti-(thioredoxin reductase) IgG and by anti-thioredoxin IgG respectively. Substitution experiments [25] showed that Escherichia coli thioredoxin could replace Fraction B. Highly purified thioredoxin reductase and thioredoxin of rat liver cytosol, together with NADPH, were shown by others to support 5'-deiodination of rT3 [25].…”

Section: Discussionmentioning

confidence: 98%

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Kinetic characteristics of a thioredoxin-activated rat hepatic and renal low-Km iodothyronine 5′-deiodinase

Bhat

Iwase

Hummel

et al. 1989

Biochemical Journal

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The properties and kinetic characteristics of a non-GSH NADPH-dependent cofactor system activating rat hepatic and renal 5'-deiodinase (5'-DI), which we have previously demonstrated with partially purified cytosol Fractions A and B [Sawada, Hummel & Walfish (1986) Biochem. J. 234, 391-398], were examined further. Although microsomal fractions prepared from either rat liver or kidneys could be activated by crude cytosol Fractions A and B from those tissues as well as from rat brain and heart, a homologous hepatic or renal system was the most potent in producing 5'-deiodination of reverse tri-iodothyronine (rT3). At nanomolar concentrations both rT3 and thyroxine (T4) were deiodinated but with a much greater substrate preference for rT3 than for T4. However, at micromolar concentrations of these substrates no activation of 5'-DI could be detected. In this deiodinative system, T4 and tri-iodothyronine (T3) competitively inhibited 5'-deiodination of rT3. Dicoumarol, iopanoate, arsenite and diamide were also inhibitory to the activation of hepatic or renal 5'-deiodination by this cofactor system. Purification of cofactor components in hepatic crude cytosolic Fractions A and B to near homogeneity, as assessed by their enzymic and physical properties, indicated that these co-purified with and were therefore identical with thioredoxin reductase and thioredoxin respectively, and accounted almost entirely for the observed activation of rT3 5'-DI. When highly purified liver cytosolic thioredoxin reductase and thioredoxin were utilized to determine the kinetic characteristics of the reaction, evidence for a sequential mechanism operative at nanomolar but not micromolar concentrations of rT3 and T4 was obtained. The Km for rT3 was 1.4 nM. Inhibition by 6-n-propyl-2-thiouracil (Ki 6.7 microM) was competitive with respect to thioredoxin and non-competitive with respect to rT3, whereas inhibition by T4 (Ki 1.3 microM) was competitive. Since rT3 is a potent inhibitor of T4 5'-deiodination, this thioredoxin system activating deiodination of rT3 may play an important role in regulating the rate of intracellular production of T3 from T4.

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Section: Discussionmentioning

confidence: 51%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

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Kinetic characteristics of a thioredoxin-activated rat hepatic and renal low-Km iodothyronine 5′-deiodinase

Bhat

Iwase

Hummel

et al. 1989

Biochemical Journal

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“…A quite analogous system as proposed now for glycine reductase might also exist for the iodothyronine 5' deiodination. The required dithiol can be replaced by the thioredoxin system (7). The respective deiodinase has recently been identified as a selenoenzyme (3).…”

Section: Discussionmentioning

confidence: 99%

Interaction of selenoprotein PA and the thioredoxin system, components of the NADPH-dependent reduction of glycine in Eubacterium acidaminophilum and Clostridium litorale [corrected]

et al. 1991

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Purification of protein PA of the glycine reductase complex from Eubacterium acidaminophUum and Clostridium litoralis was monitored by a new spectrophotometric assay. The procedure depended on a specific two-to threefold stimulation of a dihydrolipoamide dehydrogenase activity that is elicited by the interaction of a thioredoxin reductase-like flavoprotein and thioredoxin from both organisms. Protein PA isolated from E.acidaminophilum by 75 Se iabeling and monitoring of the dithioerythritol-dependent glycine reductase activity was identical in its biochemical, structural, and immunological properties to the protein isolated by using the stimulation assay. Proteins PA from both organisms were glycoproteins of Mr about 18,500 and exhibited very similar N-terminal amino acid sequences. Depletion of thioredoxin from crude extracts of E. acidaminophilum totally diminished the NADPH-dependent but not the dithioerythritol-dependent glycine reduction. The former activity could be fully restored by adding thioredoxin. Antibodies raised against the thioredoxin reductase-like flavoprotein or thioredoxin inhibited to a high extent NADPH-dependent but not dithioerythritol-dependent glycine reductase activity. These results indicate the involvement of the thioredoxin system in the electron flow from reduced pyridine nucleotides to glycine reductase.

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“…Thioredoxins were the first antioxidants identified in cells, and are known to act as general protein disulfide reductase enzymes [50] – [52] . Thioredoxins are generally maintained in a reduced state in cells by accepting protons from NADPH via the enzyme thioredoxin reductase (TrxR) [35] , [36] , [52] . In order to determine whether CLIC protein enzymatic activity is linked to the TrxR system, CLIC1, CLIC2 and CLIC4 were assayed in a system containing TrxR, in place of GR.…”

Section: Resultsmentioning

confidence: 99%

Members of the Chloride Intracellular Ion Channel Protein Family Demonstrate Glutaredoxin-Like Enzymatic Activity

et al. 2015

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The Chloride Intracellular Ion Channel (CLIC) family consists of six evolutionarily conserved proteins in humans. Members of this family are unusual, existing as both monomeric soluble proteins and as integral membrane proteins where they function as chloride selective ion channels, however no function has previously been assigned to their soluble form. Structural studies have shown that in the soluble form, CLIC proteins adopt a glutathione S-transferase (GST) fold, however, they have an active site with a conserved glutaredoxin monothiol motif, similar to the omega class GSTs. We demonstrate that CLIC proteins have glutaredoxin-like glutathione-dependent oxidoreductase enzymatic activity. CLICs 1, 2 and 4 demonstrate typical glutaredoxin-like activity using 2-hydroxyethyl disulfide as a substrate. Mutagenesis experiments identify cysteine 24 as the catalytic cysteine residue in CLIC1, which is consistent with its structure. CLIC1 was shown to reduce sodium selenite and dehydroascorbate in a glutathione-dependent manner. Previous electrophysiological studies have shown that the drugs IAA-94 and A9C specifically block CLIC channel activity. These same compounds inhibit CLIC1 oxidoreductase activity. This work for the first time assigns a functional activity to the soluble form of the CLIC proteins. Our results demonstrate that the soluble form of the CLIC proteins has an enzymatic activity that is distinct from the channel activity of their integral membrane form. This CLIC enzymatic activity may be important for protecting the intracellular environment against oxidation. It is also likely that this enzymatic activity regulates the CLIC ion channel function.

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Bacterial and mammalian thioredoxin systems activate iodothyronine 5′-deiodination

Cited by 10 publications

References 19 publications

Kinetic characteristics of a thioredoxin-activated rat hepatic and renal low-Km iodothyronine 5′-deiodinase

Kinetic characteristics of a thioredoxin-activated rat hepatic and renal low-Km iodothyronine 5′-deiodinase

Interaction of selenoprotein PA and the thioredoxin system, components of the NADPH-dependent reduction of glycine in Eubacterium acidaminophilum and Clostridium litorale [corrected]

Members of the Chloride Intracellular Ion Channel Protein Family Demonstrate Glutaredoxin-Like Enzymatic Activity

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