Title: The reaction of nitrogen monoxide with the haemocyanins of the crayfish Astacus Leptodactylus and the snail Helix Pomatia
Authors: Tahon, J-P ×
Gielens, Constant
Vinckier, Christiaan
Witters, Raphaël
De Ley, Marc
Préaux, Gisèle
Lontie, René #
Issue Date: 1989
Publisher: Pergamon
Series Title: Biochemical journal vol:262 issue:1 pages:253-260
Abstract: The rate of the reaction of Astacus leptodactylus methaemocyanin with NO follows the Henderson-Hasselbalch equation with a pKa of 5.85, suggesting that one imidazole ligand of Cu was exchanged for NO. The reaction is blocked by F- as a bridging ligand. The same imidazole residue might be responsible for the decomposition of nitrosylhaemocyanin, [Cu1NO+CuII], with an unlocated binding site for NO, into methaemocyanin and NO, as the rate increase with pH. NO could react preferentially with CuA of Helix pomatia methaemocyanin, CuA'IICuBII, as it possibly has only two histidine ligands instead of the three of CuA in Astacus haemocyanin. This difference might explain the higher formation rate and the much greater stability of Helix nitrosylhaemocyanin. The fast reaction is governed by a pKa of 6.80, probably of a bridging mu-aquo ligand. With F- or a mu-hydroxo bridging ligand a low reaction rate was still observed, in contrast with Astacus methaemocyanin. Helix nitrosylhaemocyanin was transformed by N3- into methaemocyanin with the liberation of N2 and N2O. This methaemocyanin could almost quantitatively be regenerated with H2O2. Helix nitrosylhaemocyanin was only partially regenerated by a direct treatment with H2O2 and almost quantitatively by HONH2 in a similar fairly fast reaction, followed by a much slower one.
ISSN: 0020-711X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Design and Synthesis
Biochemistry, Molecular and Structural Biology Section
× corresponding author
# (joint) last author

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