Remarkable functional aspects of myoglobin induced by diazaheme prosthetic group.
The iron complex of beta,delta-diazamesoporphyrin III, a molecular hybrid of porphyrin and phthalocyanine, was incorporated into apomyoglobin to investigate novel biological aspects of myoglobin. The reconstituted ferric protein forms an internal hemichrome with the iron-bound distal histidine. The reduced ferrous protein has extraordinarily high affinities for O2 and CO. The ferrous myoglobin is capable of strong binding with pyridine, imidazole, cyanide, and azide, and reacts moderately with ammonia. The NO complex exhibited 5-coordinate to 6-coordinate transition over 150 min. The instability of 5-coordinate NO heme is consistent with a high affinity of imidazole to the ferrous heme. The kinetic analyses of the ferrous derivatives suggest the importance of the pi orbitals in neutral ligands as well as the negative charges in anionic ligands. A high affinity of imidazole to ferrous diazaheme accounts for the internal hemochrome formation in ferrous myoglobin containing phthalocyanines.
Neya
S
S
Department of Physical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku.
Hori
H
H
Imai
K
K
Kawamura-Konishi
Y
Y
Suzuki
H
H
Shiro
Y
Y
Iizuka
T
T
Funasaki
N
N
D000143:Acids / Q000737:chemistry; D001391:Azo Compounds / Q000737:chemistry; D002248:Carbon Monoxide / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008652:Mesoporphyrins / Q000737:chemistry / Q000378:metabolism; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010795:Phthalic Acids / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry / Q000378:metabolism
D000143:Acids; D001391:Azo Compounds; D008652:Mesoporphyrins; D009211:Myoglobin; D010795:Phthalic Acids; D011166:Porphyrins; C106860:beta,delta-diazamesoporphyrin III; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D007501:Iron; D010100:Oxygen