Identification of two cytosolic ascorbate peroxidase cDNAs from soybean leaves and characterization of their products by functional expression in E. coli.

Screening of a cDNA library from soybean (Glycine max (L.) Merr. cv. Century) with probes based upon cytosolic ascorbate peroxidase (APx; EC 1.11.1.11) genes identified two full-length clones (SOYAPx1, SOYAPx2) apparently encoding for different soybean leaf cytosolic APxs. The deduced amino acid sequences of the two APx cDNA products differed in 13 of the 250 amino acids. The SOYAPx1 cDNA was identical to the cytosolic APx cDNA previously found in soybean root nodules. Escherichia coli expression systems were developed using both soybean APx cDNAs. Recombinant SOYAPx1 and SOYAPx2 were then utilized to characterize the enzymatic properties of the two APx cDNA products.