ABSTRACT
Euglenids are an ancient lineage that may have existed as early as 2 billion years ago. A mere 65 years ago, Melvin Calvin and Andrew A. Benson performed experiments on Euglena gracilis and elucidated the series of reactions by which carbon was fixed and reduced during photosynthesis. However, the evolutionary history of this pathway (Calvin-Benson cycle) in euglenids was more complex than Calvin and Benson could have imagined. The chloroplast present today in euglenophytes arose from a secondary endosymbiosis between a phagotrophic euglenid and a prasinophyte green alga. A long period of evolutionary time existed before this secondary endosymbiotic event took place, which allowed for other endosymbiotic events or gene transfers to occur prior to the establishment of the green chloroplast. This research revealed the evolutionary history of the major enzymes of the Calvin-Benson cycle throughout the euglenid lineage and showed that the majority of genes for Calvin-Benson cycle enzymes shared an ancestry with red algae and/or chromophytes suggesting they may have been transferred to the nucleus prior to the acquisition of the green chloroplast.
Subject(s)
Biological Evolution , Euglenida/enzymology , Euglenida/genetics , Photosynthesis/physiology , Aldose-Ketose Isomerases/classification , Aldose-Ketose Isomerases/genetics , Aldose-Ketose Isomerases/metabolism , Bayes Theorem , Chlorophyta/enzymology , Chlorophyta/genetics , Chlorophyta/physiology , Chloroplasts/genetics , Enzymes/classification , Enzymes/genetics , Enzymes/metabolism , Euglenida/metabolism , Fructose-Bisphosphatase/classification , Fructose-Bisphosphatase/genetics , Fructose-Bisphosphatase/metabolism , Gene Transfer, Horizontal , Glyceraldehyde-3-Phosphate Dehydrogenases/classification , Glyceraldehyde-3-Phosphate Dehydrogenases/genetics , Glyceraldehyde-3-Phosphate Dehydrogenases/metabolism , Phosphoric Monoester Hydrolases/classification , Phosphoric Monoester Hydrolases/genetics , Phosphoric Monoester Hydrolases/metabolism , Photosynthesis/genetics , Phylogeny , Rhodophyta/enzymology , Symbiosis , Triose-Phosphate Isomerase/classification , Triose-Phosphate Isomerase/genetics , Triose-Phosphate Isomerase/metabolismABSTRACT
The Pyrococcus furiosus fbpA gene was cloned and expressed in Escherichia coli, and the fructose-1,6-bisphosphatase produced was subsequently purified and characterized. The dimeric enzyme showed a preference for fructose-1,6-bisphosphate, with a K(m) of 0.32 mM and a V(max) of 12.2 U/mg. The P. furiosus fructose-1,6-bisphosphatase was strongly inhibited by Li(+) (50% inhibitory concentration, 1 mM). Based on the presence of conserved sequence motifs and the substrate specificity of the P. furiosus fructose-1,6-bisphosphatase, we propose that this enzyme belongs to a new family, class IV fructose-1,6-bisphosphatase.
Subject(s)
Archaeal Proteins/genetics , Archaeal Proteins/metabolism , Fructose-Bisphosphatase , Pyrococcus furiosus/enzymology , Amino Acid Sequence , Cloning, Molecular , Fructose-Bisphosphatase/classification , Fructose-Bisphosphatase/genetics , Fructose-Bisphosphatase/isolation & purification , Fructose-Bisphosphatase/metabolism , Molecular Sequence Data , Pyrococcus furiosus/genetics , Sequence Analysis, DNA , Substrate Specificity , TemperatureABSTRACT
Purified liver fructose 1,6-bisphosphatase exhibits different forms upon isoelectric focusing. The enzyme focused at pH 5.75, 5.60, and 5.44. Treatment of the enzyme preparation with the catalytic subunit of cAMP-dependent protein kinase and ATP altered the isoelectric focusing profile such that the bands at 5.75 and 5.60 were diminished, the band at 5.44 increased, and two new bands appeared at 5.30, and 5.18. Fructose 1,6-bisphosphatase may be present in rat liver in different forms, one of which is phosphorylated as the enzyme is isolated.
