title: Absence of synproportionation between oxy and ferryl leghemoglobin. off.
abstract: The synproportionation reaction between ferryl leghemoglobin and oxyleghemoglobin does not occur, at least under conditions where this process could be clearly demonstrated with myoglobin and hemoglobin. In contrast, a cross synproportionation can occur between oxyleghemoglobin and ferryl myoglobin or between ferryl leghemoglobin and oxymyoglobin. The non-exposure, at the surface of the leghemoglobin molecule, of the nearest tyrosine residue to the heme group could explain this behaviour. Thus leghemoglobin per se does not appear to be able to act as an antioxidant in removing H2O2 by synproportionation. However, in the presence of ascorbate and/or glutathione which can reduce ferryl leghemoglobin, this hemoprotein could act as an H2O2-removing antioxidant, in a process similar to that described for myoglobin. This could also explain why, despite the absence of synproportionation, ferryl leghemoglobin is not detected in nodule extracts.
authors.affiliation: Laboratoire de Biologie végétale et Microbiologie, URA CNRS 1114, Université de Nice-Sophia Antipolis, Nice, France.
authors.forename: C
authors.initials: C
authors.lastname: Mathieu
authors.forename: K
authors.initials: K
authors.lastname: Swaraj
authors.forename: M J
authors.initials: MJ
authors.lastname: Davies
authors.forename: J C
authors.initials: JC
authors.lastname: Trinchant
authors.forename: A
authors.initials: A
authors.lastname: Puppo
mesh_terms: D000975:Antioxidants; D001205:Ascorbic Acid; D003497:Cyclic N-Oxides / Q000737:chemistry*; D005978:Glutathione; D006861:Hydrogen Peroxide; D007700:Kinetics; D007874:Leghemoglobin / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry*; D011487:Protein Conformation; D013025:Glycine max; D013053:Spectrophotometry; D013499:Surface Properties; D014443:Tyrosine
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D007874:Leghemoglobin; C095131:oxyleghemoglobin; C015527:4-amino-TEMPO; D014443:Tyrosine; D006861:Hydrogen Peroxide; D009247:NADH, NADPH Oxidoreductases; C041176:ferric leghemoglobin reductase; D005978:Glutathione; D001205:Ascorbic Acid