bio

Rubisco

The enzyme that grabs CO₂ out of the air and attaches it to a carbon scaffold — the first committed step of carbon fixation. Everything you have ever eaten passed through it. By mass it is the most abundant protein on Earth, because it is so slow that plants must manufacture enormous quantities to compensate: Rubisco can account for a third to a half of all soluble protein in a leaf. Worse than the slowness is that it cannot reliably tell CO₂ from O₂: catching oxygen produces a useless fragment the cell must spend energy dismantling. This is a fault inherited from an era when the atmosphere held almost no oxygen, and every plant today is still stuck with it.