Phytoglobin

The earliest known phytoglobins are leghemoglobins, discovered in 1939 by Kubo after spectroscopic and chemical analysis of the red pigment of soybean root nodules.

[4] Heme-Fe coordination is essential for Phytogb (and other globins) function because it regulates the rate of ligand-binding and –releasing as consequence of the kinetic constants kon and koff, respectively.

At the same time, Lb contributes to maintain low O2-levels (~10 nM) to avoid inactivation of the O2-sensitive nitrogenase that fixes the atmospheric nitrogen.

[15] Work by Hill and collaborators during the last ~15 years has shown that levels of endogenous NO varies with the concentration of Phytogbs1 in transgenic maize and alfalfa.

Oxygenated class 1 phytoglobins reacting with NO to produce nitrate represent the main mechanism by which NO is scavenged in plants.

[17] Its operation leads to the maintenance of redox and energy status during hypoxia and results in the reduced production of ethanol and lactic acid.

[19][20][21] However, concentrations of Phytogbs increase in plants subjected to specific stress conditions, such as flooding[22] and light-limitation.

Comparative analysis of moss Phytogb0 with rice Phytogb1 and soybean Lb structure revealed that the major evolutionary changes that probably occurred during the evolution of Phytogbs0, 1 and 2, SymPhytogbs and Lbs were (i) a hexa-coordinate to penta-coordinate transition at the heme group, (ii) a length decrease at the CD-loop and N- and C-termini, and (iii) the compaction of the protein into a globular structure.

[29][30][31][32] Recently, Phytogbs were considered candidates for developing blood substitutes and as additives in veggie burgers.