MetaCyc Pathway: pentaketide chromone biosynthesis
Inferred from experimentTraceable author statement to experimental support

Pathway diagram: pentaketide chromone biosynthesis

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.

Superclasses: BiosynthesisSecondary Metabolites BiosynthesisPolyketides Biosynthesis

Some taxa known to possess this pathway include : Aloe arborescens

Expected Taxonomic Range: Magnoliophyta

General Background

Polyketide (exclusive of fatty acids) represent a large group of natural products, i.e. secondary metabolites that are widespread in fungi, bacteria and plants [Birch68, Schroder99a, Wink03]. Polyketides are often involved as intermediates in the formation of a vast variety of secondary metabolites with mixed biosynthetic origin [Schroder99b] [Schroder97a].

The entry enzymes of the biosynthesis of polyketides in plants are the polyketide synthases producing the general backbone of compounds who give rise to a large array of natural products representing an amazing degree of structural diversity. The chalcone synthase (CHS) and stilbene synthase (STS) are the most well-known plant polyketide synthases, however there exists a growing superfamily of related proteins referred to as CHS/STS-type proteins [Schroder99a]. Depending on the specific polyketide synthase involved very diverse compound classes evolve such as chalcones ( flavonoid biosynthesis), stilbenes [Schroder99b], stilbenecarboxylates [Eckermann03], benzalacetone [BorejszaWysocki96], pyrone [Eckermann98], C-methylated chalcone [Shen00] and acridone alkaloids [Baumert94] [Junghanns95].

The formation of polyketides resembles the biosynthesis of fatty acids but is different in various aspects. In contrast to fatty acid synthases (FAS) plant polyketide synthases (PKS) are relatively small homodimeric enzymes, which do not use the acyl carrier protein (ACP) as activating agent but utilize acyl-CoA esters directly as substrates [Shen00] [Birch68]. Although the synthesis of chalcone usually does not involve modifications by other proteins the chalcone derivatives reduced at a specific position in the synthesized aromatic ring are frequently found in plants increasing the structural variability of derivatives [Schroder97a]. A number of diverse type III polyketide synthases present in various plants have been cloned and found to produce diketides and heptaketides [Abe04] as well as pentaketide chromones [Abe05].

About This Pathway

The pentaketide chromone synthase (PCS) involved in the biosynthesis of 5,7-dihydroxy-2-methylchromone represents a novel type of PKSs catalyzing five successive condensations steps with malonyl-CoA as the starter unit. The product is an aromatic pentaketide chromone. The pentaketide chromone synthase (EC 2.3.1.-) isolated from aloe ( Aloe arborescens) belongs to the CHS superfamily (PKS type III). The pentaketide chromone synthase is a plant-specific, unique enzyme taking up a central function in the biosynthesis of chromones [Abe05].

Created 19-Oct-2005 by Foerster H, TAIR


Abe04: Abe I, Utsumi Y, Oguro S, Noguchi H (2004). "The first plant type III polyketide synthase that catalyzes formation of aromatic heptaketide." FEBS Lett 562(1-3);171-6. PMID: 15044020

Abe05: Abe I, Utsumi Y, Oguro S, Morita H, Sano Y, Noguchi H (2005). "A plant type III polyketide synthase that produces pentaketide chromone." J Am Chem Soc 127(5);1362-3. PMID: 15686354

Baumert94: Baumert A, Maier W, Groger D, Deutzmann R (1994). "Purification and properties of acridone synthase from cell suspension cultures of Ruta graveolens L." Z Naturforsch [C] 49(1-2);26-32. PMID: 8148006

Birch68: Birch AJ (1968). "Polyketide metabolism." Annual Review of Plant Physiology 19, 321-332.

BorejszaWysocki96: Borejsza-Wysocki W, Hrazdina G (1996). "Aromatic Polyketide Synthases (Purification, Characterization, and Antibody Development to Benzalacetone Synthase from Raspberry Fruits)." Plant Physiol 110(3);791-799. PMID: 12226219

Eckermann03: Eckermann C, Schroder G, Eckermann S, Strack D, Schmidt J, Schneider B, Schroder J (2003). "Stilbenecarboxylate biosynthesis: a new function in the family of chalcone synthase-related proteins." Phytochemistry 62(3);271-86. PMID: 12620338

Eckermann98: Eckermann S, Schroder G, Schmidt J, Strack D, Edrada RA, Helariutta Y, Elomaa P, Kotilainen M, Kilpelaeinen I, Proksch P, Teeri TH, Schroder J (1998). "New pathway to polyketides in plants." Nature 396 (26), 387-390.

Junghanns95: Junghanns KT, Kneusel RE, Baumert A, Maier W, Groger D, Matern U (1995). "Molecular cloning and heterologous expression of acridone synthase from elicited Ruta graveolens L. cell suspension cultures." Plant Mol Biol 27(4);681-92. PMID: 7727746

Schroder97a: Schroder J (1997). "A family of plant-specific polyketide synthases: facts and predictions." Trends in plant science 2(10), 373-378.

Schroder99a: Schroder J (1999). "The chalcone/stilbene synthase-type family of condensing enzymes." In: Comprehensive natural products chemistry Vol. 1: Sankawa, U. (editor), Polyketides and other secondary metabolites including fatty acids and their derivatives. Amsterdam, New York: Elsevier, 773-82323.

Schroder99b: Schroder J (1999). "Probing plant polyketide biosynthesis." Nat Struct Biol 6(8);714-6. PMID: 10426943

Shen00: Shen B (2000). "Biosynthesis of Aromatic Polyketides." Topics in Current Chemistry 209, 1-51.

Wink03: Wink M (2003). "Evolution of secondary metabolites from an ecological and molecular phylogenetic perspective." Phytochemistry 64(1);3-19. PMID: 12946402

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."

Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216

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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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