Thursday, March 14, 2013

ENZYMES : Ribulose-1,5- bisphosphate carboxylase/ oxygenase


Ribulose-1,5- bisphosphate carboxylase/ oxygenase


Active site/ reactions carried out

2D structure 
                         

Ribulose-1,5- bisphosphate molecule structure








Ribulose-1,5- bisphosphate carboxylase oxylase

  •  chemical formula:  CH2OHCO(CHOH) 2CH2OH    
  •  molar mass: 310.09 g/mol
  • ligands: Mg+2 ion 

This enzyme is commonly known by the shorter name RuBisCO,  and is an enzyme involved in the Calvin cycle that catalyzes the first major step of carbon fixation, which is the process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of energy-rich molecules such as glucose. RuBisCO is very important in terms of biological impact because it catalyzes the primary chemical reaction by which inorganic carbon permanently enters the biosphere.

 RuBisCO catalyzes either the carboxylation or the oxygenation of ribulose-1,5-bisphosphate (also known as RuBP) with carbon dioxide or oxygen.

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The reaction catalyzed by RuBisCO, with structural formulas
Carboxylation reaction
Oxygenation reaction


The rate of reaction for this enzyme is really slow compared to most enzymes. RuBisCO fixes only about three carbon dioxide molecules per second while most enzymes can process thousands of molecules per second. However plants compensate this slow rate by building lots of it. This enzyme also shows an unfortunate lack of specificity, since molecules of oxygen and carbon dioxide are similar in shape and properties, RuBisCO enzymes occasionally fix oxigen molecules to the sugar chain, forming faulty oxigenated  products.

references:
http://en.wikipedia.org/wiki/Ribulose-1,5-bisphosphate
http://guweb2.gonzaga.edu/faculty/cronk/biochem/R-index.cfm?definition=rubisco
http://guweb2.gonzaga.edu/faculty/cronk/biochem/R-index.cfm?definition=rubisco (3D ribbon structure)
http://www.climatewiki.org/wiki/Rubisco
http://www.rcsb.org/pdb/101/motm.do?momID=11