Why leghaemoglobin is considered as oxygen scavenger
Answers
Myoglobin therefore has a higher affinity for oxygen than does haemoglobin. This reflects the different functions of the two oxygen binding proteins. For example in blood capillaries (partial pressure of oxygen is approx 20 mmHg) haemoglobin will release its oxygen to myoglobin for storage there.
In plants colonised by Rhizobium, such as alfalfa or soybeans, the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase, which is an enzyme responsible for the fixation of atmospheric nitrogen. Leghemoglobin buffers the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules. Leghemoglobin has a high affinity for oxygen (Km~ 0.01 µM), about ten times higher than the β chain of human hemoglobin. This allows an oxygen concentration that is low enough to allow nitrogenase to function, but high enough that it can provide the bacteria with oxygen for respiration.