# Potential of Marine Bacterial Metalloprotease A69 in the Preparation of Antarctic Krill Peptides with Multi-Bioactivities

## TL;DR

This study explores using a marine bacterial protease to create bioactive peptides from Antarctic krill, showing strong antioxidant and enzyme-inhibiting properties.

## Contribution

The use of marine bacterial protease A69 to prepare Antarctic krill peptides with multiple bioactivities is novel and unreported previously.

## Key findings

- Peptides less than 3000 Da and 1000 Da made up 99.23% and 88.37% of the prepared AKPs.
- AKPs showed high scavenging ratios for ABTS+, DPPH·, and ·OH radicals and inhibited ACE, α-glucosidase, and DPP-IV.
- Multiple antioxidant and enzyme-inhibitory peptides were identified in the AKPs.

## Abstract

Antarctic krill (Euphausia superba) is a nutrient-rich marine resource. Although several terrestrial proteases have been used to prepare Antarctic krill peptides (AKPs), there has been no report on the preparation of AKPs using a marine protease. Here, marine bacterial protease A69 was used to prepare AKPs with multi-bioactivities. Through optimizing hydrolysis parameters, we established a process for AKPs preparation by hydrolyzing Antarctic krill powder with A69. In the prepared AKPs, peptides less than 3000 Da and 1000 Da accounted for 99.23% and 88.37%, respectively. The scavenging ratios of the AKPs to ABTS+, DPPH· and ·OH reached 93.23 ± 0.09%, 99.90 ± 0.15%, and 93.90 ± 0.47%, respectively. The AKPs also had high angiotensin-converting enzyme (ACE)-inhibitory activity, with an IC50 of 0.22 ± 0.04 mg/mL. At 40 mg/mL, the AKPs inhibited α-glucosidase and dipeptidyl peptidase IV (DPP-IV) activities by 7.18% and 13.62%, respectively, and displayed antibacterial activity to Escherichia coli. Moreover, 14 antioxidant peptides, 24 ACE-inhibitory peptides, 2 α-glucosidase-inhibitory peptides, and 10 DPP-Ⅳ-inhibitory peptides were identified from the AKPs. These results demonstrate that the prepared AKPs contain diverse bioactive peptides and have multi-bioactivities. This study indicates that marine bacterial protease A69 has promising application potential in preparing AKPs with multi-bioactivities.