Biochemical characterization of phosphoenolpyruvate carboxykinases from multiple species of brown algae
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View abstract on PubMed
Summary
This summary is machine-generated.Brown algae utilize a C4 cycle-like pathway, with their phosphoenolpyruvate carboxykinase (PEPCK) enzymes showing high activity. This study characterizes PEPCK from five brown algae, proposing a CO2 concentrating mechanism model.
Area Of Science
- Biochemistry
- Marine Biology
- Plant Physiology
Background
- Phosphoenolpyruvate carboxykinase (PEPCK) is crucial for gluconeogenesis and CO2 concentration in C4 plants.
- Brown algae possess genes for the C4 cycle and are hypothesized to use a similar pathway for CO2 concentration.
- Limited information exists on brown algal CO2-concentrating mechanisms and associated enzyme properties.
Purpose Of The Study
- To investigate the biochemical properties of PEPCK enzymes from five brown algae species.
- To elucidate the role of PEPCK in the proposed C4 cycle-like pathway in brown algae.
- To propose a model for CO2 concentration mechanisms in brown algae based on PEPCK characterization.
Main Methods
- Obtained and purified soluble recombinant PEPCKs from five brown algae species.
- Performed biochemical analyses, including specific activity measurements and kinetic studies (kcat/Km).
- Investigated the effects of various metabolites and ATP concentrations on PEPCK activity; analyzed cell extracts of *Ishige okamurae*.
Main Results
- All five recombinant PEPCKs were ATP-dependent and exhibited high specific activities, comparable to or exceeding those from other organisms.
- PEPCK from *Ishige okamurae* (Io-PEPCK) showed the highest specific activity in both carboxylation and decarboxylation, with a significantly high kcat/Km for HCO3-.
- Citrate and malate modulated Io-PEPCK activity, while ATP concentration appeared to regulate its carboxylation activity; PEPCK, not PEPC, was found to dominate carboxylation in *I. okamurae*.
Conclusions
- Brown algal PEPCKs are catalytically efficient and likely play a key role in CO2 concentration.
- Io-PEPCK exhibits unique kinetic properties suggesting specialized functions within the brown algal C4-like pathway.
- The findings support a model of a C4 cycle-like pathway in brown algae, with PEPCK as a central enzyme for CO2 concentrating mechanisms.
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