Light-Driven Oxygen Consumption in the Water-Water Cycles and Photorespiration, and Light Stimulated Mitochondrial Respiration

Raven, J; Beardall, J; Quigg, A

Light-Driven Oxygen Consumption in the Water-Water Cycles and Photorespiration, and Light Stimulated Mitochondrial Respiration

Raven, J

Beardall, J Quigg, A

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Publisher:: Springer Nature
Publication Type:: Chapter
Citation:: Photosynthesis in Algae: Biochemical and Physiological Mechanisms, 2020, pp. 161-178
Issue Date:: 2020-06-03

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Field	Value	Language
dc.contributor.author	Raven, J https://orcid.org/0000-0002-2789-3297
dc.contributor.author	Beardall, J
dc.contributor.author	Quigg, A
dc.date.accessioned	2021-02-06T20:34:21Z
dc.date.available	2021-02-06T20:34:21Z
dc.date.issued	2020-06-03
dc.identifier.citation	Photosynthesis in Algae: Biochemical and Physiological Mechanisms, 2020, pp. 161-178
dc.identifier.isbn	3030333973
dc.identifier.isbn	9783030333973
dc.identifier.uri	http://hdl.handle.net/10453/145886
dc.description.abstract	Oxygen uptake in illuminated photosynthetic algae can be measured using 18O2 or (with some reservations) photosystem II electron flux measured by fluorescence corrected for electron flux to sinks other than O2. Water-water cycles, involve photosystem II removing electrons from water to produce O2. Water-water cycles involving photosystem I as well as photosystem II use the Mehler-peroxidase reaction, or flavodiiron protein, in the O2 reduction reactions, with pumping of 3 H+ per electron. The other known water-water cycle involves only photosystem II, with the plastid (plastoquinol) terminal oxidase transferring electrons to O2, pumping of 1 H+ per electron. Return flux of the pumped H+ through the CFOCF1 ATP synthase can supplement or replace ATP from cyclic electron flow and oxidative phosphorylation in equating the supply of NADPH and ATP to the metabolic need. A further light-dependent O2 process in algae is the energy-consuming process of photorespiration metabolising 2-phosphoglycolate from Rubisco oxygenase activity. The rate of photorespiration relative to that of photosynthesis depends on the CO2:O2 selectivity of Rubisco, and the steady-state CO2:O2 ratio at the site of Rubisco. In most algae a CO2 concentrating mechanism limits photorespiration by increasing the CO2:O2 ratio at the site of Rubisco, though, in cyanobacteria at least, some photorespiratory flux is essential. The minimum rate of mitochondrial respiration in the light is set by the requirement in biosynthesis of carbon skeletons produced only in the tricarboxylic acid cycle; higher rates may occur to supply ATP. There are problems in allocating O2 uptake in the light among the various pathways; the use of inhibitors, mutants or knockouts of a particular pathway is undermined by the possibility, or even likelihood, of compensatory reactions.
dc.format.extent	18
dc.language	en
dc.publisher	Springer Nature
dc.relation.ispartof	Photosynthesis in Algae: Biochemical and Physiological Mechanisms
dc.relation.isbasedon	10.1007/978-3-030-33397-3_8
dc.rights	info:eu-repo/semantics/closedAccess
dc.title	Light-Driven Oxygen Consumption in the Water-Water Cycles and Photorespiration, and Light Stimulated Mitochondrial Respiration
dc.type	Chapter
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney
utslib.copyright.status	closed_access	*
pubs.consider-herdc	false
dc.date.updated	2021-02-06T20:34:03Z
pubs.place-of-publication	Switzerland
pubs.publication-status	Published
dc.location	Switzerland

Abstract:

Oxygen uptake in illuminated photosynthetic algae can be measured using 18O2 or (with some reservations) photosystem II electron flux measured by fluorescence corrected for electron flux to sinks other than O2. Water-water cycles, involve photosystem II removing electrons from water to produce O2. Water-water cycles involving photosystem I as well as photosystem II use the Mehler-peroxidase reaction, or flavodiiron protein, in the O2 reduction reactions, with pumping of 3 H+ per electron. The other known water-water cycle involves only photosystem II, with the plastid (plastoquinol) terminal oxidase transferring electrons to O2, pumping of 1 H+ per electron. Return flux of the pumped H+ through the CFOCF1 ATP synthase can supplement or replace ATP from cyclic electron flow and oxidative phosphorylation in equating the supply of NADPH and ATP to the metabolic need. A further light-dependent O2 process in algae is the energy-consuming process of photorespiration metabolising 2-phosphoglycolate from Rubisco oxygenase activity. The rate of photorespiration relative to that of photosynthesis depends on the CO2:O2 selectivity of Rubisco, and the steady-state CO2:O2 ratio at the site of Rubisco. In most algae a CO2 concentrating mechanism limits photorespiration by increasing the CO2:O2 ratio at the site of Rubisco, though, in cyanobacteria at least, some photorespiratory flux is essential. The minimum rate of mitochondrial respiration in the light is set by the requirement in biosynthesis of carbon skeletons produced only in the tricarboxylic acid cycle; higher rates may occur to supply ATP. There are problems in allocating O2 uptake in the light among the various pathways; the use of inhibitors, mutants or knockouts of a particular pathway is undermined by the possibility, or even likelihood, of compensatory reactions.

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http://hdl.handle.net/10453/145886