High Hydrostatic Pressure (HHP)-Induced Structural Modification of Patatin and Its Antioxidant Activities

Abstract

Patatin represents a group of homologous primary storage proteins (with molecular weights ranging from 40 kDa to 45 kDa) found in Solanum tuberosum L. This group comprises 40% of the total soluble proteins in potato tubers. Here, patatin (40 kDa) was extracted from potato fruit juice using ammonium sulfate precipitation (ASP) and exposed to high hydrostatic pressure (HHP) treatment (250, 350, 450, and 550 MPa). We investigated the effect of HHP treatment on the structure, composition, heat profile, and antioxidant potential, observing prominent changes in HHP-induced patatin secondary structure as compared with native patatin (NP). Additionally, significant (p < 0.05) increases in β-sheet content along with decreases in α-helix content were observed following HHP treatment. Thermal changes observed by differential scanning calorimetry (DSC) also showed a similar trend following HHP treatment; however, the enthalpy of patatin was also negatively affected by pressurization, and free sulfhydryl content and surface hydrophobicity significantly increased with pressurization up to 450 MPa, although both interactions progressively decreased at 550 MPa. The observed physicochemical changes suggested conformational modifications in patatin induced by HHP treatment. Moreover, our results indicated marked enhancement of antioxidant potential, as well as iron chelation activities, in HHP-treated patatin as compared with NP. These results suggested that HHP treatment offers an effective and green process for inducing structural modifications and improving patatin functionality.

Keywords: antioxidant activities; high hydrostatic pressure; iron chelation potential; potato patatin; surface hydrophobicity; thermal properties.

Figure 1

(A) Patatin purification using AKTA Protein Pure M1 and a HiTrap DEAE-sepharose FF (1 mL); (B) SDS-PAGE results showing peak 1 at MW ~20 kDa representing the protease inhibitor and peak 2 at ~40 kDa representing patatin.

Figure 2

Superdex 200 10/300 gel filtration chromatograph of peak 2 results from ion-exchange chromatography.

Figure 3

SDS-PAGE results showing NP and HHP-modified patatin under reducing conditions.

Figure 4

FTIR spectra of NP and HHP-treated patatin.

Figure 5

Flourometric results of NP and HHP-modified patatin (pH 7.0) measured at 390 nm (excitation), with emission measured between 300 nm and 800 nm. Characters (a–e) on the top of each column indicate significant differences (p < 0.05). Each data point represents the mean ± SD of triplicate treatments.

Figure 6

Free-SH content of NP and HHP-treated patatin (250–550 MPa). Characters (a–e) on the top of each column indicate significant differences (p < 0.05) difference among the groups. Results represent the mean ± SD of triplicate treatments.

Figure 7

DPPH-radical-scavenging activity of NP and HHP-treated patatin at different concentrations. Characters (a–k) on the top of each column indicate significant differences (p < 0.05). Each data point represents the mean ± SD of triplicate treatments.

Figure 8

The ORAC activity of NP and HHP-treated patatin. Characters (a–i) on the top of each column indicate significant differences (p < 0.001) among the groups. Each data point represents the mean ± SD of triplicate treatments.

Figure 9

Fe²⁺-chelating activity at different concentrations (1, 2, and 3 mg·mL⁻¹). EDTA was used as the positive control. Characters (a–l) on the top of each column indicate significant differences (p < 0.05) among the groups. All results represent the mean ± SD of each value.