Phytoene desaturase (lycopene-forming) (CrtI, ''four-step phytoene desaturase'') (, ''15-cis-phytoene:acceptor oxidoreductase (lycopene-forming)'') are

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

s found in

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

that are involved in

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

biosynthesis. They catalyze the conversion of colorless 15-''cis''-phytoene into a bright red

lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the neo-Latin ''Lycopersicum'', the tomato species) is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and vegetables. Occu ...

in a biochemical pathway called the poly-trans pathway. The same process in plants and

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

utilizes four separate enzymes in a poly-''cis'' pathway.

Biochemistry

Bacterial phytoene desaturases were shown to require FAD as a cofactor for their function. During the

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

in total four additional

double bonds In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

are introduced into phytoene: : 15-''cis''-phytoene + 4 acceptor

\rightleftharpoons

all-''trans''-lycopene + 4 reduced acceptor (overall reaction) : (1a) 15-''cis''-phytoene + acceptor

\rightleftharpoons

all-''trans''-phytofluene + reduced acceptor : (1b) all-''trans''-phytofluene + acceptor

\rightleftharpoons

all-''trans''-''zeta''-carotene + reduced acceptor : (1c) all-''trans''-''zeta''-carotene + acceptor

\rightleftharpoons

all-''trans''-neurosporene + reduced acceptor: : (1d) all-''trans''-neurosporene + acceptor

\rightleftharpoons

all-''trans''-lycopene + reduced acceptor

Applications

In 2000 it was discovered that the

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

insertion of a bacterial phytoene desaturase into transgenic tomatoes increased the lycopene content without the need to alter several of the plants enzymes. This approach was later used in

rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

to increase its

β-carotene β-Carotene is an organic, strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 ...

content resulting in the

Golden Rice Golden rice is a variety of rice (''Oryza sativa'') produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of the rice. It is intended to produce a fortified food to be grown and con ...

project.

References

External links

* {{Portal bar, Biology, border=no EC 1.3.99

Biochemistry

Applications

See also

References

External links