The α1β1 contact of human hemoglobin plays a key role in stabilizing the bound dioxygen

摘要: When the α and β chains were separated from human oxyhemoglobin (HbO2), each individual chain was oxidized easily to ferric form, their rates being almost same with a very strong acid-catalysis. In HbO2 tetramer, on other hand, both become considerably resistant autoxidation over wide range of pH values (pH 5–11). Moreover, HbA showed biphasic curve containing two rate constants, i.e. kf for fast oxidation due chains, ks slow β chains. The kf/ks ratio increased 3.2 at pH 7.5–7.3 pH 5.8, but became 1 : 1 pH values higher than 8.5. present work, we used valency hybrid tetramers such as (α3+)2(βΟ2)2 (αΟ2)2(β3+)2, demonstrated that either or (when O2-ligated) is independent state corresponding counterpart chains. From these results, have concluded formation α1β1 α2β2 contact suppresses remarkably thus plays key role in stabilizing tetramer. Its mechanistic details also given terms nucleophilic displacement O2– FeO2 center, emphasis placed proton-catalyzed process performed by distal histidine residue.