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Updated: Mar 29, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells
Published on: July 9, 2015
Assessing Low Redox Stability of Myoglobin Relative to Rapid Hemin Loss from Hemoglobin
He Cai1, Nantawat Tatiyaborworntham1, Jie Yin1
1Dept. of Animal Sciences, Meat Science and Muscle Biology Laboratory, Univ. of Wisconsin-Madison, Madison, Wiss. 53706, U.S.A.
Abstract:
Bovine myoglobin (Mb) auto-oxidized 11-fold faster at pH 5.7 compared to bovine hemoglobin (Hb). Replacement of Ser(F7) in bovine Mb with positively charged or large apolar residues decreased auto-oxidation rates (2- to 4-fold) in comparison with wild-type Mb (P < 0.05). However, the same substitutions increased hemin loss rate (15- to 28-fold), indicating that hydrogen bonding between Ser(F7) and the heme-7-propionate is critical for stabilizing protoporphyrin in the globin. The anchoring of Ser(F7) to the heme-7-propionate in the proximal pocket of Mb is suggested to expose the distal pocket to solvent molecules that accelerate auto-oxidation. The rate of hemin loss from metHb at pH 5.7 was 68-fold faster compared to metMb. The ability of Ser(F7) and His(FG3) in Mb to form stabilizing contacts with the heme-7-propionate maintains hemin within the globin whereas Leu(F7) and Leu(FG3) of Hb cannot form stabilizing contacts which results in low hemin affinity. MetHb promoted lipid oxidation more effectively in washed muscle at pH 5.7 compared to metMb (P < 0.05). The greater ability of bovine metHb to promote lipid oxidation is likely due to its enhanced rate of hemin dissociation compared to bovine metMb.
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