Insights into Common Octopus (Octopus vulgaris) Ink Proteome and Bioactive Peptides Using Proteomic Approaches

Abstract

The common octopus (Octopus vulgaris) is nowadays the most demanded cephalopod species for human consumption. This species was also postulated for aquaculture diversification to supply its increasing demand in the market worldwide, which only relies on continuously declining field captures. In addition, they serve as model species for biomedical and behavioral studies. Body parts of marine species are usually removed before reaching the final consumer as by-products in order to improve preservation, reduce shipping weight, and increase product quality. These by-products have recently attracted increasing attention due to the discovery of several relevant bioactive compounds. Particularly, the common octopus ink has been described as having antimicrobial and antioxidant properties, among others. In this study, the advanced proteomics discipline was applied to generate a common octopus reference proteome to screen potential bioactive peptides from fishing discards and by-products such as ink. A shotgun proteomics approach by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using an Orbitrap Elite instrument was used to create a reference dataset from octopus ink. A total of 1432 different peptides belonging to 361 non-redundant annotated proteins were identified. The final proteome compilation was investigated by integrated in silico studies, including gene ontology (GO) term enrichment, pathways, and network studies. Different immune functioning proteins involved in the innate immune system, such as ferritin, catalase, proteasome, Cu/Zn superoxide dismutase, calreticulin, disulfide isomerase, heat shock protein, etc., were found in ink protein networks. Additionally, the potential of bioactive peptides from octopus ink was addressed. These bioactive peptides can exert beneficial health properties such as antimicrobial, antioxidant, antihypertensive, and antitumoral properties and are therefore considered lead compounds for developing pharmacological, functional foods or nutraceuticals.

Keywords: by-product; marine natural products; mass spectrometry; protein network; protein-based bioinformatics; shotgun proteomics.

Figure 1

SDS-PAGE 10% profiles of the extracted proteins of O. vulgaris ink samples. MW denotes molecular weight.

Figure 2

Distribution of the high-abundance proteins for O. vulgaris ink samples (OVI1, OVI2, OVI3) determined by LFQ.

Figure 3

Venn diagram of the high-abundance proteins for all the O. vulgaris ink samples (OVI1, OVI2, OVI3) determined by LFQ.

Figure 4

Protein classes of the octopus ink proteome identified by shotgun proteomics and categorized by PANTHER (http://pantherdb.org/, accessed on 3 June 2022) using the homologous gene list.

Figure 5

Protein network for the common octopus ink proteome using the STRING software (v.11.5). Proteins are represented with nodes. Physical direct interactions are represented with continuous lines and functional indirect interactions with dotted lines.