Expression and characterization of the recombinant aspartic proteinase A1 from Arabidopsis thaliana

The present study reports the recombinant expression, purification, and partial characterization of a typical aspartic proteinase from Arabidopsis thaliana (AtAP A1). The cDNA encoding the precursor of AtAP A1 was expressed as a functional protein using the yeast Pichia pastoris. The mature form of the rAtAP A1 was found to be a heterodimeric glycosylated protein with a molecular mass of 47 kDa consisting of heavy and light chain components, approx. 32 and 16 kDa, respectively, linked by disulfide bonds. Glycosylation occurred via the plant specific insert in the light chain. The catalytic properties of the rAtAP A1 were similar to other plant aspartic proteinases with activity in acid pH range, maximal activity at pH 4.0, K_m of 44 μM, and k_cat of 55 s⁻¹ using a synthetic substrate. The enzyme was inhibited by pepstatin A.