Identification and partial purification of thermally stable peroxidase isoenzymes from seedlings of Vigna sp. (V) landrace Vn

Several soluble peroxidase isoenzymes are expressed in a landrace of Vigna sp. cultivated in the north of Cameroon (landrace called Vn in previous study) during seed germination. There are at least two cathodic peroxidases and eight major anodic peroxidases as shown by their electrophoretic migration at pH 7.4 under native conditions. These isoperoxidases are more expressed in roots than in shoots. They have different thermal stability, so that heat inactivation kinetics of crude peroxidase extracts from roots do not fit the first-order model. The slow and intermediate migrating groups of anodic isoperoxidases retains a substantial activity after ten minutes of incubation at 80°C and 85°C. An anodic isoperoxidase (named A6 in this study) shows in addition to this great thermal stability, a high activity in seedlings and is expressed both in roots and shoots. The combination of those characteristics makes this isoperoxidase a potential candidate for biotechnological applications. Three major anodic isoperoxidases, of which A6 and another thermostable isoperoxidase, were successfully separated from each other by ion exchange chromatography on DEAE-cellulose, after precipitation of total proteins by ice-cold acetone. This offers the prospect of being able to characterize these isoperoxidases individually in future studies.