An Arginine Aminopeptidase From Marine Bacillus Axarquiensis Swjsx8 And Its Application In Improving Pumpkin Seed Protein Hydrolysis

An arginine aminopeptidase from Bacillus axarquiensis SWJSX8 (BAAP) was developed for the first time. The enzyme was purified 16.6-fold with specificity activity of 267.2 U/mg protein and a total yield of 10.5% and was estimated to be 67.0 KDa by SDS-PAGE. It exhibited the maximum activity at 55 degrees C and pH 8.5 and was activated by 15-20% NaCl with 50% improvement. BAAP was a metalloaminopeptidase and showed better preference for Arg-pNA, Leu-pNA and Lys-pNA amongst the substrates tested. The introduction of BAAP improved the hydrolysis degree of pumpkin seed protein hydrolysates (PSPHs) by 5.7-8.2% and significantly increased the contents of small peptides and free amino acids, while decreased the bitter intensity score of the PSPHs hydrolysed by Alcalase 2.4 L. The antioxidant capacity of the PSPHs had also been improved. The newly developed BAAP has great potential to be used in hydrolysing proteins that are rich in arginine.