ISSN:
1573-5079
Keywords:
plastoquinone
;
cytochrome b-559
;
thylakoid membrane
;
Photosystem II
;
chlororespiration
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract We have found that in isolated spinach thylakoids, plastoquinone-pool (PQ-pool), after its photoreduction, undergoes dark-reoxidation with the half-time of τ1/2 = 43 ± 3 s. To explain the observed rates of PQ-pool reoxidation, a nonenzymatic plastoquinol (PQH2) autoxidation under molecular oxygen and an enzymatic oxidation by the low-potential form of cytochrome b-559 (cyt. b-559LP), as the postulated PQ-oxidase in chlororespiration, were investigated. It was found that the autoxidation rate of PQH2 in organic solvents and liposomes was too low to account for the observed oxidation rate of PQH2 in thylakoids. The rate of cyt. b-559LP autoxidation in isolated Photosystem II was found to be similar (τ1/2 = 26 ± 5 s) to that of the PQ-pool. This suggests that the LP form of cyt. b-559 is probably responsible for the PQ-oxidase activity observed during chlororespiration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006374319191
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