NADH:ubiquinone reductase (non-electrogenic) explained

NADH:ubiquinone reductase (non-electrogenic)
Ec Number:	1.6.5.9
Cas Number:	9028-04-0
Go Code:	0050136

NADH:ubiquinone reductase (non-electrogenic) (NDH-2, ubiquinone reductase, coenzyme Q reductase, dihydronicotinamide adenine dinucleotide-coenzyme Q reductase, DPNH-coenzyme Q reductase, DPNH-ubiquinone reductase, NADH-coenzyme Q oxidoreductase, NADH-coenzyme Q reductase, NADH-CoQ oxidoreductase, NADH-CoQ reductase) is an enzyme with systematic name NADH:ubiquinone oxidoreductase.^{[1] [2] [3] [4]} This enzyme catalyses the following chemical reaction:

NADH + H⁺ + a quinone

\rightleftharpoons NAD⁺ + a quinol

The 3 substrates of this enzyme are NADH, H⁺, and a quinone (electron acceptor), whereas its two products are NAD⁺ and a quinol (reduced acceptor).

An important example of this reaction is:

\rightleftharpoons NAD⁺ + ubiquinol

This enzyme is a flavoprotein (FAD). It belongs to the family of oxidoreductases, specifically those acting on NADH or NADPH with other acceptors. The systematic name of this enzyme class is NADH:(quinone-acceptor) oxidoreductase. Other names in common use include reduced nicotinamide adenine dinucleotide (quinone) dehydrogenase, NADH-quinone oxidoreductase, NADH ubiquinone oxidoreductase, DPNH-menadione reductase, D-diaphorase, and NADH2 dehydrogenase (quinone), and mitochondrial (mt) complex I. This enzyme participates in oxidative phosphorylation. Several compounds are known to inhibit this enzyme, including AMP, and 2,4-dinitrophenol. NADH dehydrogenase is involved in the first step of the electron transport chain of oxidative phosphorylation (OXPHOS). Any change in the electron transport component caused by a mutation might effect the normal electron flow. This might be leading "an increase of bifurcation and generation of superoxidase radicals and increase oxidative stress in various types of cancer cells."^[5]

In the electron transport chain NADH is mainly used to create a concentration gradient of hydrogen in order to make ATP. Since After NADH is oxidized a hydrogen is pumped out and NAD⁺ will be a product.^[6]

Structural studies

Several structures are available of this enzyme, which is part of the respiratory chain. It is a multi-subunit enzyme in which this activity is located in the hydrophilic domain. The subunits of the membrane-embedded domain are responsible for proton translocation.

Further reading

• Koli AK, Yearby C, Scott W, Donaldson KO . 1969 . Purification and properties of three separate menadione reductases from hog liver . J. Biol. Chem. . 244 . 621 - 9 . 4388793 . 4 . 10.1016/S0021-9258(18)94400-5 . free .

Notes and References

1. Direct evidence for the presence of a rotenone-resistant NADH dehydrogenase on the inner surface of plant mitochondria . Moller, I.M . Palmer, J.M. . Physiologia Plantarum . 1982 . 54 . 267–274 . 10.1111/j.1399-3054.1982.tb00258.x.
2. de Vries S, Grivell LA . Purification and characterization of a rotenone-insensitive NADH:Q6 oxidoreductase from mitochondria of Saccharomyces cerevisiae . European Journal of Biochemistry . 176 . 2 . 377–84 . September 1988 . 3138118 . 10.1111/j.1432-1033.1988.tb14292.x . free .
3. Kerscher SJ, Okun JG, Brandt U . A single external enzyme confers alternative NADH:ubiquinone oxidoreductase activity in Yarrowia lipolytica . Journal of Cell Science . 112 (Pt 14) . 14 . 2347–54 . July 1999 . 10381390 .
4. Rasmusson AG, Soole KL, Elthon TE . Alternative NAD(P)H dehydrogenases of plant mitochondria . Annual Review of Plant Biology . 55 . 23–39 . 2004 . 15725055 . 10.1146/annurev.arplant.55.031903.141720 .
5. Yusnita. Yakob. Norsiah. Md Desa. Rahman. A. Jamal. 2010-12-01. Mutations in mitochondrial NADH dehydrogenase subunit 1 (mtND1) gene in colorectal carcinoma. The Malaysian Journal of Pathology. 32. 2. 103–110. 0126-8635. 21329181.
6. Alberts. Bruce. Johnson. Alexander. Lewis. Julian. Raff. Martin. Roberts. Keith. Walter. Peter. 2002-01-01. Electron-Transport Chains and Their Proton Pumps. en.