A peroxidase purified from cowpea roots possesses high thermal stability and displays antifungal activity against Colletotrichum gloeosporioides and Fusarium oxysporum

Abstract

Plants encode specific class III peroxidases (POX) as large multigene families that are involved in lignification, cell elongation, stress defense, and seed germination. However, many functions associated with these plant enzymes are not fully understood. Here, a class III peroxidase (Vu-RPOX) was purified from cowpea (Vigna unguiculata) roots with 0–90% ammonium sulfate precipitation, chitin column and Resource Q anion-exchange chromatography. Vu-RPOX is a glycoprotein composed by a 58 kDa polypeptide chain and pI of 3.79. Two peptide sequences of Vu-RPOX (RGLDVVNDIKT and RCSTFINRL) generated by Nano ESI-Q-TOF MS/MS analysis showed variable identity with seed coat peroxidase of Glycine max, peroxidase E5 of Vigna radiata, hypothetical peroxidase of Phaseolus vulgaris, and peroxidase E5-like of Vigna unguiculata. Vu-RPOX follows the Michaelis-Menten kinetics, optimal activity at pH 6.0, and was high thermo-stable when incubated up to 75 °C for 90 min. The catalytic activity of Vu-RPOX decreased in the presence of the classic peroxidase inhibitors, but was not inhibited by MgCl2, NH4Cl, MnCl2, CaCl2, and NaCl. Vu-RPOX delay the vegetative growth of the phytopathogenic fungi Colletrotrichum gloeosporioides and Fusarium oxysporum. Based on its properties Vu-RPOX is a potentially useful molecule for application in biomedical, biotechnological, industrial, and agricultural areas particularly because it showed high stability when exposed to a wide range of temperatures and performance at pH 4–7 and impairment of mycelial growth of C. gloeosporioides and F. oxysporum.