Plastoquinone

Plastoquinone
Names
Preferred IUPAC name
2,3-Dimethyl-5-[(2E,6'E,10E,14E,18E,22E,26E,30E)-3,7,11,15,19,23,27,31,35-nonamethylhexatriaconta-2,6,10,14,18,22,26,30,34-nonaen-1-yl]cyclohexa-2,5-diene-1,4-dione
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/C53H80O2/c1-40(2)21-13-22-41(3)23-14-24-42(4)25-15-26-43(5)27-16-28-44(6)29-17-30-45(7)31-18-32-46(8)33-19-34-47(9)35-20-36-48(10)37-38-51-39-52(54)49(11)50(12)53(51)55/h21,23,25,27,29,31,33,35,37,39H,13-20,22,24,26,28,30,32,34,36,38H2,1-12H3/b41-23+,42-25+,43-27+,44-29+,45-31+,46-33+,47-35+,48-37- ☒N
    Key: FKUYMLZIRPABFK-RLAZMVNUSA-N ☒N
  • CC=1C(=O)/C=C(/C\C=C(\C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)CC\C=C(/C)C)C(=O)C=1C
Properties
C53H80O2
Molar mass 749.221 g·mol−1
Related compounds
Related compounds
 1,4-benzoquinone quinone coenzyme Q10
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Plastoquinone (PQ) is a terpenoid-quinone (meroterpenoid) molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone molecule with a side chain of nine isoprenyl units. There are other forms of plastoquinone, such as ones with shorter side chains like PQ-3 (which has 3 isoprenyl side units instead of 9) as well as analogs such as PQ-B, PQ-C, and PQ-D, which differ in their side chains.[1] The benzoquinone and isoprenyl units are both nonpolar, anchoring the molecule within the inner section of a lipid bilayer, where the hydrophobic tails are usually found.[1]

Plastoquinones are very structurally similar to ubiquinone, or coenzyme Q10, differing by the length of the isoprenyl side chain, replacement of the methoxy groups with methyl groups, and removal of the methyl group in the 2 position on the quinone. Like ubiquinone, it can come in several oxidation states: plastoquinone, plastosemiquinone (unstable), and plastoquinol, which differs from plastoquinone by having two hydroxyl groups instead of two carbonyl groups.[2]

Plastoquinol, the reduced form, also functions as an antioxidant by reducing reactive oxygen species, some produced from the photosynthetic reactions, that could harm the cell membrane.[3] One example of how it does this is by reacting with superoxides to form hydrogen peroxide and plastosemiquinone.[3]

The reduction (from left to right) of plastoquinone (PQ) to plastosemiquinone (PQH.) to plastoquinol (PQH2).

The prefix plasto- means either plastid or chloroplast, alluding to its location within the cell.[4]

  1. ^ a b Nowicka, Beatrycze; Kruk, Jerzy (2010-09-01). "Occurrence, biosynthesis and function of isoprenoid quinones". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1797 (9): 1587–1605. doi:10.1016/j.bbabio.2010.06.007. ISSN 0006-3002. PMID 20599680.
  2. ^ Tikhonov, Alexander N. (2014-08-01). "The cytochrome b6f complex at the crossroad of photosynthetic electron transport pathways". Plant Physiology and Biochemistry. 81: 163–183. doi:10.1016/j.plaphy.2013.12.011. ISSN 1873-2690. PMID 24485217.
  3. ^ a b Mubarakshina, Maria M.; Ivanov, Boris N. (2010-10-01). "The production and scavenging of reactive oxygen species in the plastoquinone pool of chloroplast thylakoid membranes". Physiologia Plantarum. 140 (2): 103–110. doi:10.1111/j.1399-3054.2010.01391.x. ISSN 1399-3054. PMID 20553418.
  4. ^ http://dictionary.reference.com/browse/Plastoquinone Definition of plastoquinone