MetaCyc Pathway: phytol salvage pathway
Inferred from experiment

Pathway diagram: phytol salvage pathway

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Synonyms: phytyl-PP biosynthesis (from phytol), phytyl-diphosphate biosynthesis (from phytol)

Superclasses: BiosynthesisSecondary Metabolites BiosynthesisTerpenoids BiosynthesisDiterpenoids Biosynthesis

Some taxa known to possess this pathway include : Arabidopsis thaliana col

Expected Taxonomic Range: Magnoliophyta

General Background

During senescence chlorophyll is degraded by chlorophyllase. This results in the release of large amounts of chlorophyllide and phytol. Although the degradation pathway of chlorophyllide (see chlorophyll a degradation I) has been the subject of a number of studies, the fate of phytol is not so clear. It has been shown that chlorophyll degradation is linked to vitamin E biosynthesis (tocopherols) during senescence, prompting the hypothesis that phytol released from chlorophyll might be channeled into tocopherol synthesis via a salvage pathway [Rise89, Peisker89]. Feeding experiments of Arabidopsis seedlings with radioactive phytol have indeed shown that, besides chlorophyll, free phytol is incorporated into tocopherol and a variety of undefined lipid esters [Ischebeck06]. Moreover, although it is unlikely that large amounts of phytol released from chlorophyll degradation be incorporated into phylloquinone, this compound was nevertheless identified as a product of phytol recycling along with the other lipid esters [Ischebeck06].

Enzymatic steps: Although both enzyme activities required for this pathway (phytol kinase and phytyl-P kinase activities) have been detected in plants, only the enzymes catalyzing the phytol kinase reaction has been isolated: a mutant involved in tocopherol biosynthesis in Arabidopsis (vte5-1) has been shown to be affected in phytyl-P formation. The gene affected by the mutation was subsequently shown to encode a protein with phytol kinase activity when heterologously expressed in Escherichia coli.

Unification Links: AraCyc:PWY-5107


Ischebeck06: Ischebeck T, Zbierzak AM, Kanwischer M, Dormann P (2006). "A salvage pathway for phytol metabolism in Arabidopsis." J Biol Chem 281(5);2470-7. PMID: 16306049

Peisker89: Peisker, C., Dggelin, T., Rentsch, D., Matile, P. (1989). "Phytol and the breakdown of chlorophyll in senescent leaves." J. Plant Physiol. 135:428-434.

Rise89: Rise, M., Cojocaru, M., Gottlieb, H.E., Goldschmidt, E.E. (1989). "Accumulation of ?-Tocopherol in Senescing Organs as Related to Chlorophyll Degradation." Plant physiol. 89: 1028-1030.

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Valentin06: Valentin HE, Lincoln K, Moshiri F, Jensen PK, Qi Q, Venkatesh TV, Karunanandaa B, Baszis SR, Norris SR, Savidge B, Gruys KJ, Last RL (2006). "The Arabidopsis vitamin E pathway gene5-1 Mutant Reveals a Critical Role for Phytol Kinase in Seed Tocopherol Biosynthesis." Plant Cell 18(1):212-24. PMID: 16361393

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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