Mn Basics
Free Fe²⁺ is dangerous because it generates these damaging radicals, and free Mn²⁺ doesn’t.
hydroxyl radicals
Photosystem II splits this molecule to release O₂
water
Catalase breaks hydrogen peroxide down into O₂ and this
water
Nitrogenase converts N₂ into this compound
Ammonia NH3
Tyr, the amino acid that acts as the electron relay in PSII
Tyrosine
Biology uses Mn in this many oxidation states
3
The antenna pigments in PSII absorb light using this molecule.
chlorophyll
Arginase splits arginine into urea and this
ornithine
Nitrogenase is irreversibly destroyed by this gas
Oxygen
Cys, the sulfur-containing amino acid that binds Mo in sulfite oxidase and helps anchor FeMoCo.
cysteine
Mn²⁺ is a close mimic of this other metal ion.
Mg²⁺
The oxygen-evolving cluster contains four Mn and one of this metal.
Calcium
Superoxide dismutase turns superoxide into O₂ and this.
hydrogen peroxide
Nitrogenase burns this many ATP per N₂ fixed.
16
His, the amino acid that binds the metal in many of these enzymes, including Mn-SOD, Mn catalase, and FeMoCo.
histidine
Unlike Fe, which is most stable as Fe³⁺, Mn is most stable in this oxidation state.
Mn2+
This S-state releases O₂ and returns the enzyme to S₀
S4
Sulfite oxidase detoxifies sulfite by converting it to this.
sulfate
Legume root nodules use this oxygen-binding protein to protect nitrogenase
Leghemoglobin
Ser, the amino acid that binds Mo in DMSO reductase.
serine
Compared to the bonds in the metal ion it replaces, Mn²⁺’s bonds to ligands are described this way.
flexible
This many light flashes (photochemical turnovers) are needed to release one O₂.
4
Xanthine oxidase converts xanthine into this final product.
uric acid
In “alternative” nitrogenases, Mo can be replaced by this metal (or by Fe).
Vanadium
Glu, the amino acid that acts as the general base in xanthine oxidase and shows up in Mn catalase and arginase
glutamate