Two cDNA clones encoding stromal (SAP28) and thylakoid-bound (SAP22) ascorbate peroxidase were isolated from a spinach cDNA library constructed by greening cotyledons. The SAP22 and SAP28 contained an open reading frame encoding mature protein of 295 and 345 amino acids with calculated molecular mass of 32 239 Da and 37 710 Da, respectively, preceded by the common transit peptides of 70 amino acid residues. Interestingly, the N-terminal 364 amino acids of SAP22 were 100% identical with SAP28 except for one C-terminal amino acid residue (Asp-365), and the C-terminal of SAP22, which is the putative transmembrane segment, was 50 amino acids longer than that of SAP28.
