Potential of Human Hemoglobin as a Source of Bioactive Peptides: Comparative Study of Enzymatic Hydrolysis with Bovine Hemoglobin and Production of Active Peptide α137-141.

Cruor, the main component responsible for the red color of blood in mammals, contains 90% hemoglobin, a protein that is considered a rich source of bioactive peptides. The aim of the present study is to evaluate the potential of human hemoglobin as a source of bioactive peptides, compared to bovine hemoglobin, which has been widely studied in recent years. More specifically, the study focused on neokyotorphin, a natural antimicrobial peptide and meat preservative, which corresponds to the α137-141 fragment of bovine hemoglobin produced by enzymatic hydrolysis. Firstly, the results of the in-silico analysis showed that the two types of hemoglobin have a high similarity for the α and β chains (identities of 88% and 91%, respectively). Secondly, both types of hemoglobin were subjected to similar enzymatic hydrolysis conditions, which showed that the hydrolysis of human hemoglobin followed the same reaction mechanism as the hydrolysis of bovine hemoglobin, the 'Zipper' mechanism. The hydrolysis conditions (23°C, pH 3.5) made it possible to obtain α137-141 in significant quantities to allow for significant valorization from an industrial point of view. The hydrolyses were able to take place at high initial substrate concentrations, allowing for faster and more efficient processing of the co-product in the same amount of time, with over 65% of this production achieved in just 30 min. Increasing the substrate concentration (from 1% to 10% (w/v)) resulted in a proportional increase in α137-141 production. Regardless of the concentrations tested, the kinetic pattern remained similar. Finally, the results of the mass spectrometry analysis revealed the presence of several bioactive peptides in cattle and humans. Although some were known before, new bioactive peptides were discovered in human hemoglobin, such as four antibacterial peptides (α37-46 PTTKTYFPHF; α36-45 FPTTKTYFPH; α137-141 TSKYR; α133-141 STVLTSKYR), four opioid peptides (α137-141 TSKYR; β31-40 LVVYPWTQRF; β31-37 LVVYPWT), an ACE inhibitor (β129-135 KVVAGVA), an anticancer agent (β33-39 VVYPWTQ) and an antioxidant (α137-141 TSKYR). These peptides have never been found in human hemoglobin before, according to our knowledge. These results highlight the potential of human hemoglobin as a source of bioactive peptides useful for the food or pharmaceutical industry.