NAD(P)+ transhydrogenase (Re/Si-specific)

 

NAD(P) transhydrogenase, a tetramer composed of 2 alpha and 2 beta subunits, is an integral membrane protein that couples the proton transport across the membrane to the reversible transfer of hydride ion equivalents between NAD and NADP. The transhydrogenation between NADH and NADP is coupled to respiration and ATP hydrolysis and functions as a proton pump across the membrane. May play a role in reactive oxygen species (ROS) detoxification in the adrenal gland.

 

Reference Protein and Structure

Sequence
Q13423 UniProt (7.1.1.1) IPR026255 (Sequence Homologues) (PDB Homologues)
Biological species
Homo sapiens (Human) Uniprot
PDB
1djl - THE CRYSTAL STRUCTURE OF HUMAN TRANSHYDROGENASE DOMAIN III WITH BOUND NADP (2.0 Å) PDBe PDBsum 1djl
Catalytic CATH Domains
3.40.50.1220 CATHdb (see all for 1djl)
Click To Show Structure

Enzyme Reaction (EC:1.6.1.2)

NADH(2-)
CHEBI:57945ChEBI
+
NADP(3-)
CHEBI:58349ChEBI
→
NAD(1-)
CHEBI:57540ChEBI
+
NADPH(4-)
CHEBI:57783ChEBI
Alternative enzyme names: H(+)-Thase, NAD transhydrogenase, NAD(P) transhydrogenase, NADH transhydrogenase, NADH-NADP-transhydrogenase, NADPH-NAD oxidoreductase, NADPH-NAD transhydrogenase, NADPH:NAD(+) transhydrogenase, Energy-linked transhydrogenase, Nicotinamide adenine dinucleotide (phosphate) transhydrogenase, Nicotinamide nucleotide transhydrogenase, Pyridine nucleotide transferase, Pyridine nucleotide transhydrogenase, Transhydrogenase, NAD(P)(+) transhydrogenase (AB-specific), NADPH:NAD(+) oxidoreductase (AB-specific),

Enzyme Mechanism

Introduction

The enzyme has three components. The dI component, which binds NAD+ and NADH, and the dIII component, which binds NADP+ and NADPH, are extrinsic proteins protruding from the membrane (on the matrix side in mitochondria and on the cytoplasmic side in bacteria), and dII spans the membrane. The enzyme is essentially a “dimer” of two dI-dII-dIII “monomers.” Studies on the transient state kinetics of transhydrogenation reveal that the redox reaction between the two nucleotides is direct. Thus, the nicotinamide and dihydronicotinamide groups are brought into apposition to allow transfer of a hydride ion equivalent between the C-4 positions of the rings. The reaction is stereo-specific for the pro-R (A-side) of NAD(H) and the pro-S (B-side) of NADP(H)

Catalytic Residues Roles

UniProt PDB* (1djl)
Arg968, Tyr1049, Tyr933 Arg925(89)A, Tyr1006(170)A, Tyr890(54)A This triad is thought to be involved in activating and stabilising the transition state of the reaction. electrostatic stabiliser
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

References

  1. Singh A et al. (2003), J Biol Chem, 278, 33208-33216. Interactions between Transhydrogenase and Thio-nicotinamide Analogues of NAD(H) and NADP(H) Underline the Importance of Nucleotide Conformational Changes in Coupling to Proton Translocation. DOI:10.1074/jbc.m303061200. PMID:12791694.
  2. Meimaridou E et al. (2012), Nat Genet, 44, 740-742. Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency. DOI:10.1038/ng.2299. PMID:22634753.
  3. Pedersen A et al. (2008), J Bioenerg Biomembr, 40, 463-473. Proton-translocating transhydrogenase: an update of unsolved and controversial issues. DOI:10.1007/s10863-008-9170-x. PMID:18972197.
  4. Obiozo UM et al. (2007), J Biol Chem, 282, 36434-36443. Substitution of Tyrosine 146 in the dI Component of Proton-translocating Transhydrogenase Leads to Reversible Dissociation of the Active Dimer into Inactive Monomers. DOI:10.1074/jbc.m705433200. PMID:17911104.
  5. Bhakta T et al. (2007), Biochemistry, 46, 3304-3318. Structures of the dI2dIII1Complex of Proton-Translocating Transhydrogenase with Bound, Inactive Analogues of NADH and NADPH Reveal Active Site Geometries†,‡. DOI:10.1021/bi061843r. PMID:17323922.
  6. Brondijk TH et al. (2006), J Biol Chem, 281, 13345-13354. The Role of Invariant Amino Acid Residues at the Hydride Transfer Site of Proton-translocating Transhydrogenase. DOI:10.1074/jbc.m513230200. PMID:16533815.
  7. Mather OC et al. (2004), Biochemistry, 43, 10952-10964. Active-Site Conformational Changes Associated with Hydride Transfer in Proton-Translocating Transhydrogenase†,‡. DOI:10.1021/bi0497594. PMID:15323555.
  8. White SA et al. (2000), Structure, 8, 1-12. The high-resolution structure of the NADP(H)-binding component (dIII) of proton-translocating transhydrogenase from human heart mitochondria. DOI:10.1016/s0969-2126(00)00075-7. PMID:10673423.
  9. Bizouarn T et al. (2000), Biochim Biophys Acta, 1457, 211-228. Proton translocating nicotinamide nucleotide transhydrogenase from E. coli. Mechanism of action deduced from its structural and catalytic properties. PMID:10773166.
  10. Olausson T et al. (1993), Biochemistry, 32, 13237-13244. Site-directed mutagenesis of tyrosine residues at nicotinamide nucleotide binding sites of Escherichia coli transhydrogenase. DOI:10.1021/bi00211a036.

Step 1.

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Catalytic Residues Roles

Residue Roles
Tyr890(54)A electrostatic stabiliser
Arg925(89)A electrostatic stabiliser
Tyr1006(170)A electrostatic stabiliser

Chemical Components

Step 1.

Contributors

James W. Murray, Craig Porter, Gemma L. Holliday