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MetNet - plant pathway - 4-hydroxybenzoate biosynthesis V
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Pathway details: 4-hydroxybenzoate biosynthesis V


General info Interaction details Linked pathways Protein-protein interactions
Notes
  Pathway was created on Mon Jul 29, 2013.
 Contributed by aracyc:
Supporting evidence for this pathway in Arabidopsis: This pathway is on the list of Accept-If-Predicted Pathways, which includes pathways that are present widely throughout the plant kingdom. [more info] Summary from MetaCyc: General Background 4-hydroxybenzoate (p-hydroxybenzoate) is widespread in plants. It is one of the major cell wall-bound phenolic acids that play a major role in plant defense against pathogens. It has also been identified as an important dietary anti-oxidant. In addition, 4-hydroxybenzoate is a key intermediate in the biosynthesis of ubiquinone-9 and several plant secondary metabolites, such as . There are at least two biosynthetic routes leading to 4-hydroxybenzoate that have been proposed in plants: 1) the beta-oxidation route that converts 4-coumarate to 4- hydroxybenzoate via 4-coumaroyl-CoA; and 2) the non-beta oxidative pathway that converts 4-coumarate to 4- hydroxybenzoate via 4- hydroxybenzaldehyde. In plants, 4- hydroxybenzoate has an origin from phenylalanine where 4-coumarate is an intermediate and cleavage of two carbons from the 4-coumarate side-chain is required , [Yazaki91],. In the beta-oxidation pathway, the side-chain shortening is analogous to fatty acid β-oxidation II (core pathway) via CoA esters. In the non-oxidative pathway, the side-chain shortening is achieved through a lyase reaction that does not require CoA as a cofactor. About This Pathway The existence of the beta-oxidation route has been reported in |CITS:. Enzyme-dependent conversion of 4-coumarate to 4-hydroxybenzoate was detected in cell-free extracts of cell cultures. The assays contained CoA, ascorbate and NAD. Under the particular assay conditions, Loscher and Heide demonstrated that 4-coumaroyl-CoA was the activated intermediate and that 4-hydroxybenzaldehyde was not an intermediate. The authors proposed that the main pathway for 4-hydroxybenzoate biosynthesis from 4-coumarate proceeded via 4-coumaroyl-CoA. In this route, 4-coumaroyl-CoA is cleaved, presumably after oxidation (analogous to fatty acid beta oxidation), in a thioclastic reaction to give rise to 4-hydroxybenzoyl-CoA and acetyl-CoA. Contrary evidence from another independent study conducted in Lithospermum erythrorhizon |CITS: [Yazaki91]|, suggested that a non-beta oxidative route also exists (see ). Although the experiments conducted by Loscher and Heide demonstrated the enzyme-dependent conversion of 4-coumaroyl-CoA to 4-hydroxybenzoate, the individual enzyme activities responsible for the sequential reactions converting 4-coumaroyl-CoA to 4-hydroxybenzoate were not specified in the study. Nonetheless, the enzymes involved appeared soluble, suggesting a cytosolic location of the pathway.
  Parts of this pathway occur in:   cytosol     mitochondrion     nucleus     peroxisome     endoplasmic reticulum  


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metabolite [19]
protein complex [6]
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polypeptide [31]
gene [21]


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