How is AOX cyanide resistant?

The alternative oxidase (AOX) is an enzyme that forms part of the electron transport chain in mitochondria of different organisms. This enzyme was first identified as a distinct oxidase pathway from cytochrome c oxidase as the alternative oxidase is resistant to inhibition by the poison cyanide.

Where does respiration take place in plants?

mitochondria
In the natural environment, plants produce their own food to survive. As with photosynthesis, plants get oxygen from the air through the stomata. Respiration takes place in the mitochondria of the cell in the presence of oxygen, which is called “aerobic respiration”.

What is cyanide resistant?

The flow of electrons in the usual mitochondrial electron transport chain (in both animals and plants) during aerobic respiration is blocked by the presence of cyanides which inhibit the activity of cytochrome oxidase. This type of respiration is known as cyanide resistant (or cyanide insensitive) respiration.

Why are plants resistant to cyanide?

How does cyanide affect aerobic respiration?

The toxicity of cyanide is linked mainly to the cessation of aerobic cell metabolism. Cyanide reversibly binds to the ferric ions cytochrome oxidase three within the mitochondria. This effectively halts cellular respiration by blocking the reduction of oxygen to water.

Which is the first site in cyanide resistant respiration?

As in conventional electron transport chain, the first phosphorylation site is coupled with electron transport chain in cyanide resistant respiration also. The physiological significance of cyanide resistant respiration is not very clear. Following roles are usually attributed to it. 1.

Why are Crabtree negative yeasts resistant to cyanide?

It has recently been shown that cyanide-resistant respiration (CRR) is very common in Crabtree-negative yeasts (incapable of aerobic fermentation) and in non-fermentative yeasts. It is conferred by a salicylhydroxamic acid-sensitive alternative oxidase that transfers electrons from ubiquinol to oxygen, bypassing the cytochrome chain.

Is there an alternative pathway to cytochrome respiration?

In plants, in many microorganisms and in most yeasts there is an alternative pathway to cytochrome respiration that transfers electrons directly from the ubiquinone pool to oxygen, bypassing complex III and cytochrome c oxidase, two sites of energy conservation in the cell.

How does CRR bypass the cytochrome chain?

It is conferred by a salicylhydroxamic acid-sensitive alternative oxidase that transfers electrons from ubiquinol to oxygen, bypassing the cytochrome chain. An interesting finding is that, in general, whenever CRR is present, complex I is also present.