MetaCyc Pathway: homogalacturonan biosynthesis

Enzyme View:

Pathway diagram: homogalacturonan biosynthesis

Note: a dashed line (without arrowheads) between two compound names is meant to imply that the two names are just different instantiations of the same compound -- i.e. one may be a specific name and the other a general name, or they may both represent the same compound in different stages of a polymerization-type 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: pectin biosynthesis

Superclasses: Biosynthesis Carbohydrates Biosynthesis Polysaccharides Biosynthesis
Biosynthesis Cell Structures Biosynthesis Plant Cell Structures Primary Cell Wall

Some taxa known to possess this pathway include ? : Arabidopsis thaliana col , Glycine max , Nicotiana tabacum , Pisum sativum

Expected Taxonomic Range: Embryophyta

Homogalacturonan (HGA) is a linear chain of 1,4-linked a-D-galacturonic acid residues in which some of the carboxyl groups are methyl esterified. HGA accounts for up to 60% of the pectin found in primary cell walls of all plants.

To synthesize HGA, UDP-galacturonate is formed from UDP-glucuronate in the cytosol. UDP- galacturonate is then transported into the Golgi by a proposed UDP- galacturonate:UMP antiporter. The galacturonate residue is transferred onto a growing HGA chain. Some of the newly added galacturonate residues are methyl esterifed at the C-6 carboxyl group. Vesicles containing the newly synthesized HGA are targeted to and fuse with the plasmamembrane thereby releasing the HGA into the exocellular space for subsequent incorporation into the wall.

Citations: [Henrik99, Sterling01, Goubet99, Ishikawa00]

Unification Links: AraCyc:PWY-1061


Goubet99: Goubet F, Mohnen D (1999). "Solubilization and partial characterization of homogalacturonan-methyltransferase from microsomal membranes of suspension-cultured tobacco cells." Plant Physiol 121(1);281-90. PMID: 10482684

Henrik99: Henrik Vibe Scheller, Ron Lou Doong, Brent Lee Ridley, Debra Mohnen "Pectin biosynthesis: a solubilized alpha 1,4-galacturonosyltransferase from tobacco catalyzes the transfer of galacturonic acid from UDP-galacturonic acid onto the non-reducing end of homogalacturonan." Planta. 1999. 207:512-517.

Ishikawa00: Ishikawa M, Kuroyama H, Takeuchi Y, Tsumuraya Y (2000). "Characterization of pectin methyltransferase from soybean hypocotyls." Planta 210(5);782-91. PMID: 10805450

Ron98: Ron Lou Doong, Debra Mohnen "Solubilization and characterization of a galacturonosyltransferase that synthesizes the pectin polysaccharide homogalacturonan." The Plant Journal. 1998. 13(3):363-374.

Sterling01: Sterling JD, Quigley HF, Orellana A, Mohnen D (2001). "The catalytic site of the pectin biosynthetic enzyme alpha-1,4-galacturonosyltransferase is located in the lumen of the Golgi." Plant Physiol 127(1);360-71. PMID: 11553763

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."

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Mon Mar 30, 2015, BIOCYC13B.