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Leghemoglobin
From Wikipedia, the free encyclopedia
The oxygen carrier leghemoglobin (also legoglobin) is a hemoprotein found in the nitrogen-fixing root nodules of leguminous plants. It is produced by legumes in response to the roots being infected by the nitrogen-fixing bacterium, rhizobium, as part of the symbiotic interaction between plant and bacterium: roots uninfected with Rhizobium do not synthesise leghemoglobin. Leghemoglobin has close chemical and structural similarities to hemoglobin, and, like hemoglobin, is red in colour. The protein is a product of both plant and the bacterium; the apoprotein is produced by the plant and the heme (an iron atom bound in a porphyrin ring) is produced by the bacterium.
In plants infected with Rhizobium, (such as alfalfa or soybeans), the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase. Leghemoglobin buffers the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules.
See also: hemoglobin, myoglobin
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