Leghemoglobin (also
leghaemoglobin or
legoglobin) is a nitrogen or oxygen carrier, because naturally occurring oxygen and nitrogen interact similarly with this protein; and a
hemoprotein found in the
nitrogen-fixing root nodules of
leguminous plants. It is produced by legumes in response to the roots being colonized by nitrogen-fixing bacteria, termed
rhizobia, as part of the
symbiotic interaction between plant and bacterium: roots not colonized by
Rhizobium do not synthesise leghemoglobin. Leghemoglobin has close chemical and structural similarities to
hemoglobin, and, like hemoglobin, is red in colour. The holoprotein (protein + heme cofactor) is widely believed to be a product of both
plant and the
bacterium in which the apoprotein is produced by the plant and the
heme (an iron atom bound in a
porphyrin ring) is produced by the
bacterium. There is some evidence, however, that suggests that the heme moiety is also produced by the plant.