Kinetics and molecular docking studies of the inhibition of arginase by lupin seed protein-derived peptides

Arginase dysregulation is implicated in various pathological conditions, including cardiovascular diseases, erectile dysfunction, and cancer, making it an attractive therapeutic target. In this study, enzymatic hydrolysates of white lupin ( Lupinus albus ) and blue lupin ( Lupinus angustifolius ) protein isolates were evaluated for arginase-inhibitory activity. Among the hydrolysates tested, white lupin flavourzyme hydrolysate exhibited the highest inhibitory potency (∼35% at 800 μg/mL), followed by trypsin and pepsin hydrolysates, while alcalase hydrolysates showed no activity. Reverse-phase HPLC fractionation followed by tandem mass spectrometry identified ten peptide sequences from the most active fractions. Two structurally distinct peptides, the short hydrophobic hexapeptide DMGAVA and the long polycationic 16-mer VVALKKVGVLKKPGPT, demonstrated the highest arginase inhibition and were selected for mechanistic studies. Lineweaver-Burk analysis revealed mixed-type inhibition kinetics with distinct profiles: DMGAVA substantially affected both Km and Vmax (Ki ∼266 μM), whereas VVALKKVGVLKKPGPT showed predominantly competitive behavior with minimal change in Vmax (Ki ∼589 μM).