Heterologous expression and characterization of a proxidomal ascorbate peroxidase from Populus tomentosa.

The present study reported for the first time, cloning, expression and characteristics of a Proxidomal APX gene (PpAPX) from Populus tomentosa. The PpAPX gene encodes a protein of 287 amino acid residues with a calculated molecular mass of 31.58 kDa. The over-expressed recombinant PpAPX protein showed high activity towards the substrates ascorbate aicd (ASA) and H(2)O(2). At fixed ASA concentrations, the K (m) and V (max) values were 0.12 +/- 0.01 mM and 23.4 +/- 4.2 mmol/min mg for H(2)O(2). And at fixed H(2)O(2) concentrations, the K (m) and V (max) values were 0.53 +/- 0.04 mM and 20.0 +/- 2.3 mmol/min mg for ASA.