Physico-Chemical and Antifungal Properties of a Trypsin Inhibitor from the Roots of Pseudostellaria heterophylla

Abstract

Plant peptidase inhibitors play essential roles in the defense systems of plants. A trypsin inhibitor (PHTI) with a molecular mass of 20.5 kDa was isolated from the fresh roots of the medicinal herb, Pseudostellaria heterophylla. The purification process involved ammonium sulfate precipitation, gel filtration chromatography on Sephadex G50, and ion-exchange chromatography on DEAE 650M. The PHTI contained 3.7% α-helix, 42.1% β-sheets, 21.2% β-turns, and 33% disordered structures, which showed similarity with several Kunitz-type trypsin inhibitors. Inhibition kinetic studies indicated that PHTI was a competitive inhibitor, with a Ki value of 3.01 × 10−9 M, indicating a high affinity to trypsin. The PHTI exhibited considerable stability over a broad range of pH (2–10) and temperatures (20–70 °C); however, metal ions, including Fe3+, Ba2+, Mn2+, and Al3+, could inactivate PHTI to different degrees. Results of fluorescence spectroscopy and circular dichroism showed that Fe3+ could bind to TI with an association constant of 2.75 × 105 M−1 to form a 1:1 complex, inducing conformation changes and inactivation of PHTI. In addition, PHTI could inhibit the growth of the phytopathogens, Colletotrichum gloeosporioides and Fusarium oxysporum, through disruption of the cell membrane integrity. The present study extended research on Pseudostellaria heterophylla proteins and makes PHTI an exploitable candidate as an antifungal protein for further investigation.

Allelopathic potential of root exudates from perennial herbaceous plants against Ganoderma boninense

“…However, the literature described trypsin inhibitors present as allelochemicals in root exudates of X. sagittifolium [20] that may function to suppress the growth of root rot fungi. A trypsin inhibitor secreted by roots of the medicinal herb, Pseudostellaria heterophylla could inhibit growth of the phytopathogens, Colletotrichum gloeosporioides and Fusarium oxysporum [21]. C. indica roots secreted a high concentration of allelochemical organic acids and have been reported to play in inhibition against the blue-green algae Microcystis aeruginosa [22][23].…”

Valorization of Okara by Enzymatic Production of Anti-Fungal Compounds for Plant Protection

“…From both the experiments reported in Figure 6 and Figure 7 , it is evident that OPI itself, at different extents, exerts an inhibitory activity on mycelial growth in dependence either of the fungal strain or the protein concentration. It is reported that trypsin inhibitors may exert antifungal activity as a plant defense response [ 24 , 25 , 26 ]. Thus, the dose-response dependent inhibition activity of OPI samples is likely attributable to TIA.…”

Bowman-Birk Major Type Trypsin Inhibitor Derived from Foxtail Millet Bran Attenuate Atherosclerosis via Remodeling Gut Microbiota in ApoE–/– Mice

“…The activity of trypsin inhibitors of the various stages of purification was measured using BAPNA. The method was used from X. Cai et al 25 with some modifications.…”