Phytoene () is a 40-carbon intermediate in the biosynthesis of

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 ...

s. The synthesis of phytoene is the first committed step in the synthesis of carotenoids in plants. Phytoene is produced from two molecules of

geranylgeranyl pyrophosphate Geranylgeranyl pyrophosphate is an intermediate in the biosynthesis of diterpenes and diterpenoids. It is also the precursor to carotenoids, gibberellins, tocopherols, and chlorophylls. It is also a precursor to geranylgeranylated proteins, whi ...

(GGPP) by the action of the enzyme

phytoene synthase Phytoene synthase (, ''prephytoene-diphosphate synthase'', ''15-cis-phytoene synthase'', ''PSase'', ''geranylgeranyl-diphosphate geranylgeranyltransferase'') is a transferase enzyme involved in the biosynthesis of carotenoids. It catalyzes the con ...

. The two GGPP molecules are condensed together followed by removal of diphosphate and proton shift leading to the formation of phytoene. Dietary phytoene and phytofluene are found in a number of human tissues including the liver, lung, breast, prostate, colon, and skin. Accumulation of these carotenoids in the skin may protect the skin by several mechanisms: acting as UV absorbers, as antioxidants, and as anti-inflammatory agents.

Structure

Phytoene is a symmetric molecule containing three

conjugated double bond In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases Chemical stability, stability. It is Resonance ...

s. Phytoene has a UV-Vis absorption spectrum ''typical'' for a triply conjugated system with its main absorption maximum in the

UVB Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

range at 286 nm and with '' ε1% of 915''.

Sources

Analysis of several fruits and vegetables showed that phytoene and

phytofluene Phytofluene is a colorless carotenoid found naturally in tomatoes and other vegetables. It is the second product of carotenoid biosynthesis. It is formed from phytoene in a desaturation reaction leading to the formation of five conjugated doubl ...

are found in majority of fruits and vegetables. In contrast to all other carotenoids, phytoene and phytofluene, the first carotenoid precursors in the biosynthetic pathway of other carotenoids, absorb light in the UV range.

History

The structure of phytoene was established and proven by total synthesis, by the

Basil Weedon Professor Basil Charles Leicester Weedon CBE, FRS (18 July 1923 – 10 October 2003) was an organic chemist and university administrator. Using nuclear magnetic resonance spectroscopy, he was the first to map the structures of carotenoid pigme ...

group in 1966.

References

{{carotenoids 7. Book chapter: Liki von Oppen-Bezalel, Aviv Shaish. Application of the Colorless Carotenoids, Phytoene, and Phytofluene in Cosmetics, Wellness, Nutrition, and Therapeutics. In The alga Dunaliella: Biodiversity, Physiology, Genomics & Biotechnology. Eds. Ami Ben-Amotz, Juergen Polle, and Subba Rao, released May 2009 by Science Publishers, Enfield, NH, USA (2009) Carotenoids Tetraterpenes Substances discovered in the 1960s