The effect of pH on the initial-rate kinetic behaviour of BVR-A (biliverdin-IXα reductase) exhibits an alkaline optimum with NADPH as cofactor, but a neutral optimum with NADH as cofactor. This has been described as dual cofactor and dual pH dependent behaviour; however, no mechanism has been described to explain this phenomenon. We present evidence that the apparent peak of activity observed at neutral pH with phosphate buffer and NADH as cofactor is an anion-dependent activation, where inorganic phosphate apparently mimics the role played by the 2′-phosphate of NADPH in stabilizing the interaction between NADH and the enzyme. The enzymes from mouse, rat and human all exhibit this behaviour. This behaviour is not seen with BVR-A from Xenopus tropicalis or the ancient cyanobacterial enzyme from Synechocystis PCC 6803, which, in addition to being refractory to activation by inorganic phosphate, are also differentiated by an acid pH optimum with both nicotinamide nucleotides.
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Research Article|
June 13 2007
Activation of biliverdin-IXα reductase by inorganic phosphate and related anions
Edward Franklin;
Edward Franklin
1
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
1To whom correspondence should be addressed (email efrankli@tcd.ie).
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Seamus Browne;
Seamus Browne
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Jerrard Hayes;
Jerrard Hayes
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Coilin Boland;
Coilin Boland
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Aisling Dunne;
Aisling Dunne
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Gordon Elliot;
Gordon Elliot
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Timothy J. Mantle
Timothy J. Mantle
1School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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Publisher: Portland Press Ltd
Received:
November 03 2006
Revision Received:
March 19 2007
Accepted:
April 03 2007
Accepted Manuscript online:
April 03 2007
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 2007 Biochemical Society
2007
Biochem J (2007) 405 (1): 61–67.
Article history
Received:
November 03 2006
Revision Received:
March 19 2007
Accepted:
April 03 2007
Accepted Manuscript online:
April 03 2007
Citation
Edward Franklin, Seamus Browne, Jerrard Hayes, Coilin Boland, Aisling Dunne, Gordon Elliot, Timothy J. Mantle; Activation of biliverdin-IXα reductase by inorganic phosphate and related anions. Biochem J 1 July 2007; 405 (1): 61–67. doi: https://doi.org/10.1042/BJ20061651
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