Copper-chelating peptide from salmon by-product proteolysate

Abstract

The aims of this study included evaluation of copper-binding capacity (CBC) and amino acid composition of salmon by-product proteolysate and its peptide fractions, optimization of hydrolysis condition, and identification of copper-binding peptides from the proteolysate. The result was that under the ideal hydrolysis (Neutrase, temperature of 45 °C, pH 7, enzyme:substrate (E:S) proportion of 72.24 U/g protein and hydrolysis time of 8.02 h), the proteolysate had the indispensable amino acid content at approximately 38.7% and also displayed the maximal CBC of 15163.6 µg Cu2+/g protein. Besides, four peptide fractions of 10–30 kDa, 3–10 kDa, 1–3 kDa, and <1 kDa were recovered using ultrafiltration, among which the <1 kDa fraction had the highest CBC of 10852.00 ± 895.06 µgCu2+/g protein. A copper-binding peptide, Phe-Ile-Asp-Asp-Asp-Ala-Phe-Ile-Arg (1110 Da), was identified from this fraction using tandem mass spectrometry (MS/MS). As a whole, the proteolysate/peptides could be used for copper enhancement that could shield human body from copper inadequacy disorders.

An investigation into copper-binding capacity of the white leg shrimp head (Litopenaeus vannamei) protein hydrolysate

“…The method of Vo and Pham [6] was used to assess the CBC of WLSH protein hydrolysate. 1ml of protein hydrolysate was added to the mixture of 1ml of 2mM CuSO4 solution, 1ml of 10% pyridine solution and 20µl of 0.1% pyrocatechol violet solution.…”

“…In this study, CBC of the proteolysate peaked at 8.5±0.5 mg Cu 2+ /g protein at the temperature of 50 o C, optimal temperature (Figure 1c). Under the effect of temperature, the conformation change of substrate and enzyme revealed the hydrophobic or electrondonating amino acid side chains inside the substrate [6], boosting the formation and stabilization of coordination bond between peptides and copper ions. At non-optimal temperature, due to the decrease in their movement or change in their configuration, the interaction between enzyme and substrate molecules was diminished, reducing the formation of copper-binding peptides.…”

“…It was obvious from figure 4 that when boosting the E:S ratio from 80 to 90 U/g protein, there was a significant decrease in CBC. Vo and Pham [6] assumed that through early steps of hydrolysis, larger quantity of enzyme could degrade high potential copper-binding peptides forming, reducing CBC of protein hydrolysate. Hence, the E:S ratio of 80 U/g protein was used for further analyses.…”

“…Similarly, Asp stimulated the CBC of the protein hydrolysate by donating free electrons in O-carboxyl to Cu 2+ empty orbitals [7]. Moreover, nitrogen atoms in -imidazole ring of His and/or in Ɛ-amide of Lys are acted as electron donors that stimulates the CBC of the protein hydrolysate [6,7]. With the presence of S-containing amino acids, e.g.…”

“…As a way to tackle these problems, the presence of chelator was reported from Osborn-Barnes and Akoh [5] to inhibit metal-catalyzed oxidation reaction. Some copper-binding peptides have been found to be potential chelators from aquatic life forms and by-products [6,7].…”