Rubisco

Rubisco (or ribulose-1.5-biphosphate carboxylase/oxygenase) is a plant enzyme involved in the Calvin cycle, specifically in binding carbon dioxide .

Rubisco is found in the chloroplasts and is the most abundant protein in the plant biomass, and even in the total biomass.

It generally consists of two types of protein subunits coded for by two different genes, large (L for large) and smaller (S for small) each type of complete rubisco having eight subunits. The active sites are generally located on the large subunits.

Rubisco is involved in the photosynthesis process and has two enzymatic activities:

• a carboxylase activity through which rubisco binds a CO₂ onto D-ribulose-1.5-diphosphate to form two molecules as 3-phospho-D-glycerate;
• an oxygenase activity through which rubisco binds a molecule of O₂ onto D-ribulose-1.5-diphosphate to form 3-phospho-D-glycerate and 2-phosphoglycolate.

Rubisco therefore plays an active role in the carbon cycle.