Lysine Lactylation of Hemoglobin Promotes Oxygen Release in Red Blood Cells

Hemoglobin oxygen affinity (HOA) increases during the storage of red blood cells (RBCs), which hinders the oxygen-release efficacy after transfusion. RBCs stored in alkaline preservation solution promote glycolysis and its final product lactate, which is an allosteric regulator of HOA. In recent years, lactylation has been widely studied, and the degree of lactylation is positively associated with the lactate concentration. However, it is unclear whether lactate can participate in the allosteric regulation of HOA via lactylation when lactate accumulates to a certain level during RBC storage in alkaline preservation solutions. Therefore, we prepared preservation solutions with the same formulation but different pH values and investigated the changes in P₅₀, which represent HOA, and lactate levels. We also performed comprehensive analysis on the lactylation of stored RBCs via molecular dynamics simulation and confirmed the effects of lactylation on hemoglobin (Hb) via in vitro experiments. We found lactylation modifications in RBCs and less storage damage when stored in alkaline preservation solutions. Lactylation acts predominantly on the lysine 66 site of the Hb β-subunit. Lactylation promotes conformational changes of Hb from the relaxed (R) state to the tight (T) state, which in turn promotes oxygen release from RBCs.