Leghemoglobin

Part of speech: noun

Definitions

1. A red protein found in the root nodules of leguminous plants that binds oxygen and helps nitrogen-fixing bacteria function
2. An oxygen-carrying pigment present in the nodules of peas, beans and other legumes that protects nitrogen fixation from damage
3. A plant hemoglobin-like protein located in legume root nodules that transports and regulates oxygen for symbiotic bacteria

Etymology: Leghemoglobin is a twentieth-century coinage, not an ancient or classical word. It was built in the 1930s and 1940s from two parts: "leg-", short for "leguminous", meaning the legume plant family, and "hemoglobin", the oxygen-carrying protein of blood. The name tells you where the protein was found: in the root nodules of legumes such as peas, beans and clover, where it was first identified in the 1930s and 1940s. The protein's job is unusual. Nitrogen-fixing bacteria living inside the nodules need oxygen to work, but the enzyme that fixes nitrogen is destroyed by too much of it. Leghemoglobin binds oxygen the way blood hemoglobin does, keeping the free oxygen level low while still delivering enough for the bacteria's respiration. The plant makes it, and the bacteria supply the nitrogen, so the molecule sits at the centre of one of the best-known partnerships in plant biology.