Multiple choice The most abundant protein found on Earth is PEP caroxylase RUBISCO Aldolase Transketolase Reveal answer Fill a bubble to check yourself B Correct answer Explanation RUBISCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is Earths most abundant protein. It catalyzes carbon fixation in photosynthetic organisms plants, algae, cyanobacteria comprising up to 50% of leaf soluble protein.