NAD(P)+ transhydrogenase (Si-specific)

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NAD(P)+ transhydrogenase (Si-specific)
EC number
CAS number 9014-18-0
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

In biochemistry, NAD(P)+ transhydrogenase (Si-specific) (EC is an enzyme that catalyzes the chemical reaction


Thus, the two substrates of this enzyme are NADPH and NAD+, whereas its two products are NADP+ and NADH. This enzyme participates in nicotinate and nicotinamide metabolism. It employs one cofactor, FAD.

Physiological function[edit]

Si-specific transhydrogenase is a soluble protein found in some Gammaproteobacteria and gram-positive bacteria. Enterobacteriaceae are known to possess both a soluble and a membrane-bound transhydrogenase.[1] In living cells this enzyme primarily operates in the direction consuming NADPH and producing NADH, as the physiological ratio of NADPH/NADP+ is much higher than the ratio of NADH/NAD+.[1] Its chief function in vivo is the reoxidization of excess NADPH.[2]


This enzyme belongs to the family of oxidoreductases, specifically those acting on NADH or NADPH with NAD+ or NADP+ as acceptor. The systematic name of this enzyme is NADPH:NAD+ oxidoreductase (Si-specific). Other names in common use include non-energy-linked transhydrogenase, NAD(P)+ transhydrogenase (B-specific), and soluble transhydrogenase.

Older literature often uses ambiguous names such as pyridine nucleotide transhydrogenase, transhydrogenase, NAD(P)+ transhydrogenase, nicotinamide nucleotide transhydrogenase, NADPH-NAD+ transhydrogenase, pyridine nucleotide transferase, or NADPH-NAD+ oxidoreductase, which can equally apply to the more common NAD(P)+ transhydrogenase (Re/Si-specific).


  1. ^ a b Cao Z, Song P, Xu Q, Su R, Zhu G (Jul 2011). "Overexpression and biochemical characterization of soluble pyridine nucleotide transhydrogenase from Escherichia coli". FEMS Microbiology Letters. 320 (1): 9–14. doi:10.1111/j.1574-6968.2011.02287.x. PMID 21545646. 
  2. ^ Sauer U, Canonaco F, Heri S, Perrenoud A, Fischer E (Feb 2004). "The soluble and membrane-bound transhydrogenases UdhA and PntAB have divergent functions in NADPH metabolism of Escherichia coli". The Journal of Biological Chemistry. 279 (8): 6613–9. doi:10.1074/jbc.M311657200. PMID 14660605. 

Further reading[edit]

  • You KS (1985). "Stereospecificity for nicotinamide nucleotides in enzymatic and chemical hydride transfer reactions". CRC Critical Reviews in Biochemistry. 17 (4): 313–451. doi:10.3109/10409238509113625. PMID 3157549.