Recombinant Prochlorococcus marinus Glucose-6-phosphate isomerase (pgi), partial
Description
Functional Role in Prochlorococcus Metabolism
PGI is central to both glycolysis and the oxidative pentose phosphate pathway (PPP). In P. marinus SS120, glucose uptake activates pgi expression, linking it to mixotrophic growth strategies under fluctuating nutrient conditions . Key metabolic interactions include:
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Glycolysis: Converts G6P to F6P, feeding into fructose-1,6-bisphosphate synthesis .
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PPP: Supplies NADPH and ribose-5-phosphate via G6P oxidation .
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Ecological adaptation: Enables carbon flexibility in oligotrophic oceans, where organic carbon scavenging complements photosynthesis .
Enzymatic Activity and Kinetic Parameters
While kinetic data for recombinant P. marinus PGI are not explicitly reported, inferred properties from related PGIs include:
| Parameter | Value (Representative) | Source Organism |
|---|---|---|
| Optimal temperature | 70–80°C (thermophilic homologs) | Pyrococcus furiosus |
| Kₘ (G6P) | 0.2–0.5 mM | Eukaryotic/bacterial PGIs |
| pH optimum | 7.0–7.5 | E. coli |
The enzyme likely exhibits lower thermostability than archaeal homologs due to P. marinus’ mesophilic habitat .
Genomic and Proteomic Insights
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Genomic conservation: The pgi gene is part of the core genome in Prochlorococcus, retained across high-light (e.g., MED4) and low-light (e.g., SS120) ecotypes .
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Regulatory links: Co-expressed with zwf (glucose-6-phosphate dehydrogenase) and gnd (6-phosphogluconate dehydrogenase) under glucose supplementation .
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Horizontal gene transfer (HGT): No evidence of pgi acquisition via HGT in Prochlorococcus, unlike Microcystis strains where pgi duplication occurs .
Research Implications and Applications
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Metabolic engineering: Recombinant PGI could optimize carbon flux in cyanobacterial biofuel production .
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Ecological modeling: Understanding PGI’s role in mixotrophy improves predictions of Prochlorococcus responses to oceanic carbon cycling .
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Biotechnological potential: Structural studies of partial PGI may aid in designing inhibitors for pathogenic homologs .
Product Specs
Target Background
KEGG: pme:NATL1_09931
STRING: 167555.NATL1_09931
