Home ยป What is RuBisCO?

What is RuBisCO?

If you want to understand the mechanics of photosynthesis, you have to understand RuBisCO, Ribulose-1,5-bisphosphate carboxylase/oxygenase.

RuBisCO is said to be the most common protein on the planet. One recent study estimated there are around 700 Megatons of RuBisCO on Earth. This figure is about twice the mass of the whole human race, all as one enzyme.

The reason there’s so much of it around is that RuBisCO is a protein found in all photosynthetic organisms, from plants to bacteria. It’s used by all organisms that photosynthesise carbon dioxide into hydrocarbons for energy and growth.

It’s difficult to overstate RuBisCO’s importance. Each year it fixes over 100 gigatons of carbon by pulling about 450 gigatons of carbon dioxide out of the atmosphere. It’s the key enzyme in keeping the planet’s ecosystem running for everything else to live.

Despite being crucial for life, RuBisCO is not very good at its job. RuBisCO developed before Earth’s atmosphere had much oxygen, so recognising and rejecting oxygen was not a problem for photosynthetic species. Unfortunately, RuBisCO is very happy to react with oxygen, a process known as photorespiration, and while it’s doing that, it’s not cracking carbon dioxide. One estimate is that around 35 per cent of the time, RuBisCO binds with oxygen instead of carbon dioxide. This process is a waste of energy and reduces the efficiency of photosynthesis, reducing plant growth and yield.

For this reason, scientists around the world are working to improve the efficiency of RuBisCO. One reason for improving RuBisCO efficiency is to improve plant yields, allowing them to spend more time harvesting energy from the sun and less time wasting it. It may also be necessary so that plants can cope with the stresses of a warming climate. However, some research suggests that photorespiration may benefit plants in stabilising the Calvin Cycle to manage photosynthetic rates and reduce stress on cells.

A diagram showing the phases of the Calvin Cycle, with RuBisCO prominently labelled in the 'picks up Carbon Dioxide' section.
An overview of the Calvin Cycle. Image: Mike Jones / Wikimedia Commons

The potential benefits of improving RuBisCO are enormous. It may be possible to gain more food for less human work, secure a food supply and reduce the landmass used for agriculture. A plant with reduced energy needs could also be a massive boon to space exploration, proving that, for botanists, the sky isn’t the limit.

Alun Salt

Alun (he/him) is the Producer for Botany One. It's his job to keep the server running. He's not a botanist, but started running into them on a regular basis while working on writing modules for an Interdisciplinary Science course and, later, helping teach mathematics to Biologists. His degrees are in archaeology and ancient history.

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