Kinetics of NADP+/NADPH reduction–oxidation catalyzed by the ferredoxin-NAD(P)+ reductase from the green sulfur bacterium Chlorobaculum tepidum
Ferredoxin-NAD(P) + oxidoreductase (FNR, [EC 1.18.1.2], [EC 1.18.1.3]) from the green sulfur bacterium Chlorobaculum tepidum ( Ct FNR) is a homodimeric flavoprotein with significant structural homology to bacterial NADPH-thioredoxin reductases. Ct FNR homologs have been found in many bacteria, but o...
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Published in | Photosynthesis research Vol. 130; no. 1-3; pp. 479 - 489 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Dordrecht
Springer Netherlands
01.12.2016
|
Subjects | |
Online Access | Get full text |
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Summary: | Ferredoxin-NAD(P)
+
oxidoreductase (FNR, [EC 1.18.1.2], [EC 1.18.1.3]) from the green sulfur bacterium
Chlorobaculum tepidum
(
Ct
FNR) is a homodimeric flavoprotein with significant structural homology to bacterial NADPH-thioredoxin reductases.
Ct
FNR homologs have been found in many bacteria, but only in green sulfur bacteria among photoautotrophs. In this work, we examined the reactions of
Ct
FNR with NADP
+
, NADPH, and (4
S
-
2
H)-NADPD by stopped-flow spectrophotometry. Mixing
Ct
FNR
ox
with NADPH yielded a rapid decrease of the absorbance in flavin band I centered at 460 nm within 1 ms, and then the absorbance further decreased gradually. The magnitude of the decrease increased with increasing NADPH concentration, but even with ~50-fold molar excess NADPH, the absorbance change was only ~45 % of that expected for fully reduced protein. The absorbance in the charge transfer (CT) band centered around 600 nm increased rapidly within 1 ms, then slowly decreased to about 70 % of the maximum. When
Ct
FNR
red
was mixed with excess NADP
+
, the absorbance in the flavin band I increased to about 70 % of that of
Ct
FNR
ox
with an apparent rate of ~4 s
−1
, whereas almost no absorption changes were observed in the CT band. Obtained data suggest that the reaction between
Ct
FNR and NADP
+
/NADPH is reversible, in accordance with its physiological function. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0166-8595 1573-5079 |
DOI: | 10.1007/s11120-016-0285-3 |