Action Spectra for Photosystems I and II in Formaldehyde Fixed Algae

Ludlow, C. Joseph; Park, Roderic B.

doi:10.1104/pp.44.4.540

Cited by 27 publications

(5 citation statements)

References 14 publications

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“…The final concentration of H 4 F was determined by measuring the A 297 , applying an extinction coefficient of 27 mM Ϫ1 cm Ϫ1 (41). Solutions of formaldehyde (5 to 20 mM) were also made fresh shortly before use by heating paraformaldehyde suspended in 100 mM potassium phosphate buffer (22). The assay was started by adding 100 l of 5 to 20 mM formaldehyde to 900 l of 10 to 20 M H 4 F in a 1-ml cuvette.…”

Section: H-labeling Experiments Incorporation Of Deuterium (mentioning

confidence: 99%

Formate as the Main Branch Point for Methylotrophic Metabolism in Methylobacterium extorquens AM1

Crowther¹,

Kosály²,

2008

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In serine cycle methylotrophs, methylene tetrahydrofolate (H 4 F) is the entry point of reduced one-carbon compounds into the serine cycle for carbon assimilation during methylotrophic metabolism. In these bacteria, two routes are possible for generating methylene H 4 F from formaldehyde during methylotrophic growth: one involving the reaction of formaldehyde with H 4 F to generate methylene H 4 F and the other involving conversion of formaldehyde to formate via methylene tetrahydromethanopterin-dependent enzymes and conversion of formate to methylene H 4 F via H 4 F-dependent enzymes. Evidence has suggested that the direct condensation reaction is the main source of methylene H 4 F during methylotrophic metabolism. However, mutants lacking enzymes that interconvert methylene H 4 F and formate are unable to grow on methanol, suggesting that this route for methylene H 4 F synthesis should have a significant role in biomass production during methylotrophic metabolism. This problem was investigated in Methylobacterium extorquens AM1. Evidence was obtained suggesting that the existing deuterium assay might overestimate the flux through the direct condensation reaction. To test this possibility, it was shown that only minor assimilation into biomass occurred in mutants lacking the methylene H 4 F synthesis pathway through formate. These results suggested that the methylene H 4 F synthesis pathway through formate dominates assimilatory flux. A revised kinetic model was used to validate this possibility, showing that physiologically plausible parameters in this model can account for the metabolic fluxes observed in vivo. These results all support the suggestion that formate, not formaldehyde, is the main branch point for methylotrophic metabolism in M. extorquens AM1.Methylobacterium extorquens AM1 is a facultative methylotroph that has served as a model system for understanding methylotrophic metabolism for many decades (1,3,33). One outstanding question in methylotrophic metabolism involves the route by which C 1 compounds are incorporated into assimilatory metabolism. In this bacterium, methanol or methylamine is oxidized via formaldehyde and formate to CO 2 for energy metabolism and carbon is assimilated via the serine cycle ( Fig.

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Section: H-labeling Experiments Incorporation Of Deuterium (mentioning

confidence: 99%

Formate as the Main Branch Point for Methylotrophic Metabolism in Methylobacterium extorquens AM1

Crowther¹,

Kosály²,

2008

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“…The extinction coefficients of Gantt and Lipschultz 1974 may have been underestimated (Glazer and Hixon, 1975) and therefore R-PC and APC values may be underestimates. of chlorophyll a,, activity (Cederstrand et al, 1966;Ludlow and Park, 1969).…”

Section: Discussionmentioning

confidence: 99%

PHOTOSYNTHETIC ACTION SPECTRA AND LIGHT‐HARVESTING IN GRIFFITHSIA MONILIS (RHODOPHYTA)

Larkum

Weyrauch

1977

Photochem & Photobiology

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In cells of the red alga Grifithsia monilis the action spectrum of photosynthetic oxygen production at low light intensity shows that the phycobilins (including allophycocyanin) are the major light-harvesting pigments. As the light intensity is increased carotenoids and chlorophyll a contribute proportionately more to the spectrum, since the phycobilin activity becomes light-saturated. When action spectra are performed against a background light of various monochromatic wavelengths it can be shown that chlorophyll a increases in its light-harvesting activity. Nevertheless light absorbed at a single wavelength (487 nm) by phycoerythrin (and possibly a carotenoid) still shows the highest photosynthetic activity. Fluorescence measurements at 77K indicate that a chlorophyll a fluorescence is small and that the amount of chlorophyll all (f 693) is very low. A model is proposed in which the phycobilins, in phycobilisomes, pass on absorbed light energy to either photosystem, whereas light absorbed by chlorophyll is passed on mainly to photosystem I. 65PAP. 25/1-~

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“…also 266-269). A photosystem II-mediated photoreduction of DCPIP is observed with aldehyde-fixed Anacystis (340,522).…”

Section: Fig 10 Polyhedral Body Frommentioning

confidence: 93%

Physiology and cytological chemistry blue-green algae.

Wölk¹

1973

Bacteriological Reviews

189

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Action Spectra for Photosystems I and II in Formaldehyde Fixed Algae

Cited by 27 publications

References 14 publications

Formate as the Main Branch Point for Methylotrophic Metabolism in Methylobacterium extorquens AM1

Formate as the Main Branch Point for Methylotrophic Metabolism in Methylobacterium extorquens AM1

PHOTOSYNTHETIC ACTION SPECTRA AND LIGHT‐HARVESTING IN GRIFFITHSIA MONILIS (RHODOPHYTA)

Physiology and cytological chemistry blue-green algae.

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