## 2 Results and Discussion
### Identification of Peptides in Viscera Extracts
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Protein of Origin of the** & **Identified Peptide** & **Sequence** & **Obs MW** & **Obs \(m\)/z** & **Theor z** \\ \hline Uncharacterized protein y4 iR 2-C-methyl-D-erythitol 4-phosphate-cytridyltransferase & & & & \\ Zinc finger CZIC domain-containing & & & & \\ protein 1A & & & & \\ Trichadiene synthase & & & & \\
60 kDa heat shock protein, mitochondrial & & & & \\ pH-response regulator protein palF/RIMS & & & & \\ Leucine-rich repeat-containing protein 56 & & & & \\ Tungsten-containing & & & & \\ formylmethanolofuran- & & & & \\ dehydrogenase 2 subunit C & & & & \\ Cyclic pyranopterin & & & & \\ monophosphate synthase & & & & \\ Acetylcholinesteraseterase & & & \\ Uncharacterized pre-PGRS family & & & & \\ protein PE & & & & \\ Sulfocyanin & & & & \\ Actin, cytoplasmic & & & & \\
40S ribosomal protein S3a & & & & \\ DNA repair protein crb2 & & & & \\ Arginousuccinate synthase & & & & \\ Collagen alpha-2(I) chain & & & & \\ Thiazole synthase & & & & \\ GlyLLNTAVSGAKDP & & & \\ Histone-lysine N-methyltransferase transferase 2D & & & & \\ Probable transcriptional regulatory & & & & \\ protein Ecaj\_0351 & & & & \\
50S ribosomal protein L29 & & & & \\  & & & \\ Forkhead box protein K1 & & & & \\ Probable GPI-anchored adhesin-like & & & & \\ protein PGA32 & & & & \\ Replicase polyprotein 1 ab & & & \\ Stonin-2 & & & & \\ SLAIN motif-containing protein & & & \\ Structural maintenance of chromosomes & & & & \\ protein 4 & & & \\ Golgiin-84 & & & & \\ Keratin, type II cytoskeletal 5 & & & \\ Translation initiation factor IF-2 & & & & \\ Genome polyprotein & & & \\ Collagen alpha-1(X) chain & & & & \\ Transcription-associated protein 1 & & & \\ MAM and LDL-receptor class A domain-containing & & & \\ containing: protein 2 & & & \\ Coiled-coil domain-containing & & & \\ protein CG32809 & & & & \\ Large teggument protein denedylase & & & \\ Adenylyl cyclase-associated protein & & & & \\ Neuroblast differentiation-associated & & & \\ protein AHNAK & & & \\ Mediator of RNA polymerase II & & & \\ transcription subunit 28 & & & \\ Protein S100 & & & & \\ LisH domain-containing protein & & & \\ Adenylyl cyclase-associated protein & & & \\ Guanylate cyclase & & & \\ domain-containing protein & & & \\ Insulin receptor substrate 2 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cont. A common method currently used to speculate about peptide function is through an amino acid homology alignment against a database of known functional peptide sequences. The antioxidant activity of the identified peptides was thus predicted using the BIOPEP-UWM database, which is a bioinformatics tool for searching among bioactive peptides, mainly derived from foods [28]. None of the peptides identified in salmon viscera extracts were found among the antioxidant peptides inputted in the BIOPEP-UMP database. Therefore, a new search based on the profiles of the potential biological activity of peptides was performed. BIOPEP-UWM analysis results exhibited several antioxidant small peptides encrypted in amino acid sequences of PLE (Table 3) and control (Table 4) viscera extracts, with some of them known to be derived from marine species. Throughout the entire structure of peptides, 19 different sequences of peptides with antioxidant activity were found in the PLE extract, whereas there were 12 in the control extract. Most of these potential antioxidant peptides were di- and tri-peptides. The sequence GPP was found in 15 peptides of the PLE extract, followed by GAA, which was found in five peptides. These sequences could be responsible for antioxidant activity, since antioxidant peptides from marine resources have been described to contain hydrophobic acids such as glycine (G), proline (P), and alanine (A) [8; 9; 29]. Furthermore, salmon antioxidant peptides from the pectoral fin (FLNEFLFUV) and trimmings (GGPAGPAV, GPVA, PP, GP) have been reported [10; 30].