Can you guess what the most abundant protein in the world is? Is it collagen, the protein that composes the connective tissues in mammals? Or is it actin, a microfilament that plays a vital role in the processes of cell division and muscle contraction? Nope. The most abundant protein on planet Earth is the enzyme ribulose biphosphate carboxylase/oxygenase (or rubisco for short). This enzyme catalyzes the reaction of carbon dioxide with a molecule abbreviated RuBP to produce a 3-carbon sugar abbreviated 3PG in the Calvin cycle of photosynthesis. This is quite amazing if you ask me. But not that surprising. Autotrophs form the literal foundation of Earth's biosphere, using the radiant energy of the sun to reduce electron carriers and produce ATP for the production of glucose. Science never ceases to amaze me, especially biochemistry. It is quite a miracle and marvel that life has persisted for so many millennia under the operation of such meticulous microsystems.