World Library  
Flag as Inappropriate
Email this Article

Phaseic acid

Article Id: WHEBN0023146637
Reproduction Date:

Title: Phaseic acid  
Author: World Heritage Encyclopedia
Language: English
Subject:
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Phaseic acid

Phaseic acid
Identifiers
Jmol-3D images Image 1
Properties
Molecular formula C15H20O5
Molar mass 280.31 g/mol
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Phaseic acid is a terpenoid catabolite of abscisic acid. Like abscisic acid, it is a plant hormone associated with photosynthesis arrest[1] and abscission.

Function

Abscisic acid (ABA) is a multifunctional plant hormone, playing roles in germination, seasonal growth patterns, and stress response. ABA levels are believed to be regulated in part by control of ABA catabolism, specifically by oxidation to form phaseic acid.[2] Phaseic acid can therefore be thought of as a degradation product of ABA, although it may have other functions. The introduction of high phaseic acid concentrations have been found to impede stomatal closure and reduce photosynthesis in arabidopsis[1] but this may be a result of product inhibition rather than recognition of phaseic acid by a receptor.

Biosynthesis

Early precursors

Phaseic acid is an isoprenoid, which means that it is derived from isoprene units. The activated terpene geranylgeranyl pyrophosphate is combined with itself to produce the common carotenoid precursor, lycopene.



Carotenoid precursors

Phaseic acid is a product of abscisic acid, which is itself the product of the C40 carotenoid zeaxanthin via at least four enzymatic steps. Zeaxanthin is epoxidized by to form violaxanthin or neoxanthin. The C15 end of the molecule is then cleaved by an epoxycarotenoid epoxygenase to form xanthoxin, an aldehyde.


Modification of xanthoxin

Xanthoxin is reduced at the epoxy group and then hydroxylated at the aldehyde group, producing abscisic acid.[3] The 8' hydroxylation of abscisate, abscisic acid's conjugate base, produces 8'-hydroxyabscisate. 8'-hydroxyabscisate cyclizes via nucleophilic attack of the existing ring by the 8' hydroxy group to interconvert with phaseate. The former process is known to be mediated by 8' abscisic acid hydroxylases, a family of NADPH-dependent enzymes. Saito et al. have demonstrated that, in the case of arabidopsis, these hydroxylases are independent of any regulatory mechanism downstream of translation itself.[4][5] The latter process is reported to occur without enzymatic intervention,[4][6] as it has been found to occur spontaneously in vitro.

References

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.