Purification and stability of a basic peroxidase from strawberry callus culture

A basic isoperoxidase from strawberry (Fragaria x ananassa cv. Chandler) ca llus culture was purified by sequential CM-Cellulose, Concanavalin-A Sephar ose 4B and Sephacryl S-200 chromatographies. Isoelectrofocusing of the puri fied peroxidase activity revealed the presence of one unique basic isoperox idase (Faprx1, pI 9.2). Native cathodic electrophoresis and SDS-PAGE analys is of the basic isoenzyme yielded a single protein band. The molecular mass of the basic isoenzyme estimated by SDS-PAGE and matrix-assisted laser des orption ionisation time-of-flight (MALDI-TOF) mass spectrometry was 35 and 32.6 kDa, respectively. The low molecular mass of the isoenzyme may be due to the low degree of glycosylation of its polypeptide chain. Faprx1 showed unusual instability even at room temperature. The effects of bovine serum a lbumin (BSA), Ca2+, hematin and pH on the stability of the basic isoperoxid ase were assayed. The presence of the three stabilising agents showed a rem arkable protective effect on Faprx1 activity in a wide pH range. (C) 2001 E ditions scientifiques et medicales Elsevier SAS.