HISTIDINE OXIDATION IN THE OXYGEN-EVOLVING PHOTOSYSTEM-II ENZYME
HISTIDINE OXIDATION IN THE OXYGEN-EVOLVING PHOTOSYSTEM-II ENZYME
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DOI：
10.1038/347303a0
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发表时间：
1990-09-20
期刊：
影响因子：
64.8
通讯作者：
LAVERGNE, J
中科院分区：
文献类型：
--
作者：
BOUSSAC, A;ZIMMERMANN, JL;LAVERGNE, J
THE evolution of oxygen as a result of light-driven water oxidation occurs in plants and is catalysed by photosystem-II (PS-II). A manganese-cluster probably acts both as the active site and as a charge-accumulating device (for a review, see ref. 1). The enzyme cycle involves five redox states which are denoted as S0–S4, depend-ing on the number of positive equivalents stored2. Oxygen is released after formation of the transient S4state. Ca2+is an obligatory cofactor in this process and its depletion inhibits the enzyme cycle at the step before water oxidation, that is, after formation of the S3state3. In chelator-treated, Ca2+-depleted PS-II, a new electron paramagnetic resonance (EPR) signal arising from a formal S3state has been reported4. It was suggested that the S3EPR signal could originate from the oxidation of an amino acid, interacting magnetically with the manganese cluster4. There are only a few examples of amino-acid oxidation in enzyme chemistry and these are limited to tyrosine5and tryptophan6. Here we report evidence that the S2to S3transition occurring in Ca2+-depleted PS-II corresponds to the oxidation of histidine.
