Phytoene synthase explained

15-cis-phytoene synthase
Ec Number:	2.5.1.32
Cas Number:	50936-61-3

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 conversion of geranylgeranyl pyrophosphate to phytoene.^{[1] [2] [3] [4]} This enzyme catalyses the following chemical reaction

\rightleftharpoons 15-cis-phytoene + 2 diphosphate (overall reaction)

(1a) 2 geranylgeranyl diphosphate

\rightleftharpoons diphosphate + prephytoene diphosphate

(1b) prephytoene diphosphate

\rightleftharpoons 15-cis-phytoene + diphosphate

This enzyme requires Mn²⁺ for activity. It belongs to squalene/phytoene synthase family of proteins.

Notes and References

1. http://www.brenda-enzymes.org/php/result_flat.php4?ecno=2.5.1.32 Phytoene synthase
2. Gregonis DE, Rilling HC . The stereochemistry of trans-phytoene synthesis. Some observations on lycopersene as a carotene precursor and a mechanism for the synthesis of cis- and trans-phytoene . Biochemistry . 13 . 7 . 1538–42 . March 1974 . 4819767 . 10.1021/bi00704a033 .
3. Chamovitz . Daniel . Misawa . Norihiko . Sandmann . Gerhard . Hirschberg . Joseph . Molecular cloning and expression in of a cyanobacterial gene coding for phytoene synthase, a carotenoid biosynthesis enzyme . FEBS Letters . 27 January 1992 . 296 . 3 . 305–310 . 10.1016/0014-5793(92)80310-d.
4. Misawa N, Truesdale MR, Sandmann G, Fraser PD, Bird C, Schuch W, Bramley PM . Expression of a tomato cDNA coding for phytoene synthase in Escherichia coli, phytoene formation in vivo and in vitro, and functional analysis of the various truncated gene products . Journal of Biochemistry . 116 . 5 . 980–5 . November 1994 . 7896759 .