Iron also biological significance

Recent studies suggest that many factors may affect hydroxyl radical generation by microsomes. Reinke et al. [34] demonstrated that the hydroxyl radical-mediated oxidation of ethanol in rat liver microsomes depended on phosphate or Tris buffer. Cytochrome bs can also participate in the microsomal production of hydroxyl radicals catalyzed by NADH-cytochrome bs reductase [35,36]. Considering the numerous demonstrations of hydroxyl radical formation in microsomes, it becomes obvious that this is not a genuine enzymatic process because it depends on the presence or absence of free iron. Consequently, in vitro experiments in buffers containing iron ions can significantly differ from real biological systems. 

Similarly, the lower accessibility of tyrosyl residues to base titration in ferric lactoferrin compared to ferric transferrin has been suggested to be linked to their relative stabilities as metallocomplexes 67, 163). Ferric conalbumin also appears to be more stable than ferric transferrin 157). These stability differences may be of biological significance given that a role of the serum protein is to distribute iron in the body rather than to sequester the metal. 

Iron salts and iron-EDTA also catalyze the generation of highly reactive radicals from superoxide Thus, low ferric iron and superoxide are often termed to be deleterious to the cell. This problem is leading to the last section of this article, namely the biological significance of the dismutation of superoxide. 

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