Conformational stability of a peroxidase from Artocarpus lakoocha: Effect of pH, chaotrophs and temperature.

A novel heme-peroxidase has been extracted from the latex of the medicinal plant Artocarpus lakoocha (A. lakoocha), known for its potential anti-inflammatory and wound healing properties. To study its stability, structure, and dynamics, this protein was analyzed using far-UV circular dichroism, fluorescence spectroscopy, and activity measurements. The results demonstrated the presence of three folding states: the native state (N) at neutral pH, intermediate states including molten globule (MG) at pH 2 and acid-unfolded (UA) at pH 1.5 or lower, and acid-refolded (A) at pH 0.5, along with alkaline denatured (UB) at pH 8-12 and the third denatured state (D) at GuHCl concentrations exceeding 5 M. Absorbance studies indicated the presence of free heme in the pH range of 1-2. The protein showed stability and structural integrity across a wide pH range (3-10), temperature (70 {degrees}C), and high concentrations of GuHCl (5 M) and urea (8 M). This study is the first to report multiple partially folded intermediate states of A. lakoocha peroxidase, with varying amounts of secondary structure, stability, and compactness. These results demonstrate the high stability of A. lakoocha peroxidase and its potential for biotechnological and industrial applications, making it a valuable model system for further studies on its structure-function relationship.