TY - JOUR
T1 - Catalase-free photosystem II
T2 - The O2-evolving complex does not dismutate hydrogen peroxide
AU - Sheptovitsky, Yelena G.
AU - Brudvig, Gary W.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1998/4/14
Y1 - 1998/4/14
N2 - A photosystem II (PSII) membrane-associated heme catalase has been identified as a major source of the dark H2O2-dismutation reaction in PSII membrane samples [Sheptovitsky, Y. G., and Brudvig, G. W. (1996) Biochemistry 35, 16255-16263]. Based on this finding, a catalase-free PSII membrane sample was prepared by using mild heat treatment to deplete most of the PSII membrane-associated heme catalase followed by inhibition of the residual catalase with 50 mM 3-amino-1,2,4-triazole, a specific heme catalase inhibitor that binds covalently to compound I. After these treatments, the PSII membrane sample exhibited only 0.02% of the original H2O2-dismutation activity when assayed in the presence of 20 mM 3-amino-1,2,4-triazole. This small residual H2O2-dismutation activity is attributed to adventitious metal ions or the non-heme iron in PSII because the activity was still present in a Mn-depleted PSII sample but was completely suppressed by adding 5 mM ferricyanide to the assay buffer; the effect of ferricyanide is attributed to oxidation of H2O2-dismutating cations. Although the H2O2- dismutation activity was completely eliminated by these treatments, the light-induced O2-evolution activity was retained. A single saturating flash given to catalase-free PSII membranes did not induce any H2O2-dismutation activity. These results demonstrate that the S1/S-1 and S2/S0 cycles of the O2-evolving complex of PSII do not occur in the presence of H2O2, as proposed by Velthuys, B., and Kok, B. [(1978) Biochim. Biophys. Acta 502, 211-221]. The light-induced O2-evolution activity in catalase-free PSH was found to be irreversibly impaired by micromolar concentrations of H2O2. Thus, it is possible that the PSII membrane-associated heme catalase plays an important role in protection of the O2-evolving complex from damage by H2O2.
AB - A photosystem II (PSII) membrane-associated heme catalase has been identified as a major source of the dark H2O2-dismutation reaction in PSII membrane samples [Sheptovitsky, Y. G., and Brudvig, G. W. (1996) Biochemistry 35, 16255-16263]. Based on this finding, a catalase-free PSII membrane sample was prepared by using mild heat treatment to deplete most of the PSII membrane-associated heme catalase followed by inhibition of the residual catalase with 50 mM 3-amino-1,2,4-triazole, a specific heme catalase inhibitor that binds covalently to compound I. After these treatments, the PSII membrane sample exhibited only 0.02% of the original H2O2-dismutation activity when assayed in the presence of 20 mM 3-amino-1,2,4-triazole. This small residual H2O2-dismutation activity is attributed to adventitious metal ions or the non-heme iron in PSII because the activity was still present in a Mn-depleted PSII sample but was completely suppressed by adding 5 mM ferricyanide to the assay buffer; the effect of ferricyanide is attributed to oxidation of H2O2-dismutating cations. Although the H2O2- dismutation activity was completely eliminated by these treatments, the light-induced O2-evolution activity was retained. A single saturating flash given to catalase-free PSII membranes did not induce any H2O2-dismutation activity. These results demonstrate that the S1/S-1 and S2/S0 cycles of the O2-evolving complex of PSII do not occur in the presence of H2O2, as proposed by Velthuys, B., and Kok, B. [(1978) Biochim. Biophys. Acta 502, 211-221]. The light-induced O2-evolution activity in catalase-free PSH was found to be irreversibly impaired by micromolar concentrations of H2O2. Thus, it is possible that the PSII membrane-associated heme catalase plays an important role in protection of the O2-evolving complex from damage by H2O2.
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U2 - 10.1021/bi972872s
DO - 10.1021/bi972872s
M3 - Article
C2 - 9548736
AN - SCOPUS:0032515935
VL - 37
SP - 5052
EP - 5059
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 15
ER -