title: Analysis and elucidation of phosphoenolpyruvate carboxylase in cyanobacteria.
abstract: Phosphoenolpyruvate carboxylase (PEPC) a cytosolic enzyme of higher plants is also found in bacteria and cyanobacteria. Genetic and biochemical investigations have indicated that there are several isoforms of PEPC belonging to C3; C3/C4 and C4 groups but, the evolution of PEPC in cyanobacteria is not yet understood. The present study opens up an opportunity to understand the isoforms and functions of PEPC in cyanobacteria. The variations observed in PEPC among lower and higher orders of cyanobacteria, suggests convergent evolution of PEPC. There is a specific PEPC phosphorylation residue 'serine' at the N-terminus and PEPC determinant residue 'serine' at the C-terminal that facilitates high affinity for substrate binding. These residues were unique to higher orders of cyanobacteria, but, not in lower orders and other prokaryotes. The different PEPC forms of cyanobacteria were investigated for their kinetic properties with phosphoenolpyruvate as the substrate and the findings corroborated well with the in silico findings. In vitro enzymatic study of cyanobacteria belonging to three different orders demonstrated the role of aspartate as an allosteric effector, which inhibited PEPC by interacting with the highly conserved residues in the active site. The differences in mode of inhibition among the different order, thus, give a fair picture about the cyanobacterial PEPCs. The higher orders appear to possess the sequence coordinates and functionally conserved residues similar to isoforms of C4 type higher plants, whereas isoforms of PEPC of the lower orders did not resemble either that of C3 or C4 plants.
authors.affiliation: National Facility for Marine Cyanobacteria (Sponsored by DBT, Govt. of India), Department of Marine Biotechnology, School of Marine Sciences, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India.
authors.forename: Mohandass
authors.initials: M
authors.lastname: Shylajanaciyar
authors.forename: Gnanasekaran
authors.initials: G
authors.lastname: Dineshbabu
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Rajalakshmi
authors.forename: Gopalakrishnan
authors.initials: G
authors.lastname: Subramanian
authors.forename: Dharmar
authors.initials: D
authors.lastname: Prabaharan
authors.forename: Lakshmanan
authors.initials: L
authors.lastname: Uma
mesh_terms: D046870:Anabaena variabilis / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D048929:Prochlorococcus / Q000201:enzymology / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D019764:Phosphoenolpyruvate Carboxykinase (ATP)