Necessary Components of NPQ (qE)
1. pH gradient
2. Conversion of Violaxanthin to Zeaxanthin1
? Epoxidase Enzyme: ideal pH = 8.0
? Depoxidase Enzyme: ideal pH = 5.2
3. PsbS (a.k.a. CP22)2
2X.P. Li, et al., Nature, 2000, 403, 391.
1P. Müller, et al., Plant Physiology, 2001, 125, 1558.
Zeaxanthin
Antheraxanthin
Violaxanthin
excess
h?
excess
h?
limiting
h?
limiting
h?
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