Salmonids are an incredibly valuable agricultural commodity, with large market growth expected over the next 10 years. Salmonids have a high feed conversion ratio and are rich in vital nutrients; however, their post-mortem tissues are subject to deterioration due in part to their labile hemoglobin (Hb). In this work, we aimed to understand the driving force for the pro-oxidative nature of salmonid (trout IV) Hb. We utilized resonance Raman spectroscopy (rR), electronic absorption spectroscopy (EA), and density functional theory (DFT) calculations to probe the distal and proximal heme pocket architectures of trout IV and bovine Hb. Using fluoride as a H-bond-sensitive ligand, we found that at low pH, trout IV ferric Hb is more likely to have a protonated distal His. The enhanced distal His protonation and mobility play a crucial role in hemin dissociation, explaining the oxidative capacity of salmonid Hb, which dwarfs that of mammalian Hb.
Baker et al. (Fri,) studied this question.