RubisCO, the CO2fixing enzyme of the Calvin–Benson–Bassham (CBB) cycle, is responsible for the majority of carbon fixation on Earth. RubisCO fixes12CO2faster than13CO2resulting in13C‐depleted biomass, enabling the use of δ13C values to trace CBB activity in contemporary and ancient environments. Enzymatic fractionation is expressed as an
- Award ID(s):
- 1952676
- NSF-PAR ID:
- 10300376
- Editor(s):
- Atomi, Haruyuki
- Date Published:
- Journal Name:
- Applied and Environmental Microbiology
- Volume:
- 87
- Issue:
- 17
- ISSN:
- 0099-2240
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary ε value, and is routinely used in modelling, for example, the global carbon cycle and climate change, and for interpreting trophic interactions. Although values for spinach RubisCO (ε = ~29‰) have routinely been used in such efforts, there are five different forms of RubisCO utilized by diverse photolithoautotrophs and chemolithoautotrophs andε values, now known for four forms (IA, B, D and II), vary substantially withε = 11‰ to 27‰. Given the importance ofε values in δ13C evaluation, we measured enzymatic fractionation of the fifth form, form IC RubisCO, which is found widely in aquatic and terrestrial environments. Values were determined for two model organisms, the ‘Proteobacteria’ Ralstonia eutropha (ε = 19.0‰) andRhodobacter sphaeroides (ε = 22.4‰). It is apparent from these measurements that all RubisCO forms measured to date discriminate less than commonly assumed based on spinach, and that enzymeε values must be considered when interpreting and modelling variability of δ13C values in nature. -
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