cDNA, amino acid and carbohydrate sequence of barley seed-specific peroxidase BP 1

peptide, targeting The major peroxidase of barley seed BP 1 was characterized. Previous studies showed a low carbohy-drate content, low specific activity and tissue-specific expression, and suggested that this basic peroxi-dase could be particularly useful in the elucidation of the structure-function relationship and in the study of the biological roles of plant peroxidases (S.K. Rasmussen, K.G. Welinder and J. Hejgaard (1991) Plant Mol Biol 16: 317-327). A cDNA library was prepared from mRNA isolated from seeds 15 days after flowering. Full-length clones were obtained and showed 3 ' end length variants, a G + C content of 69~o in the translated region, a 90~o G or C preference in the wobble position of the codons and a typical signal peptide sequence. N-terminal amino acid sequencing and sequence analysis of tryptic peptides verified 98 ~o of the sequence of the mature BP 1 which contains 309 amino acid residues. BP 1 is the first characterized plant peroxidase which is not blocked by pyroglutamate. BP 1 polymorphism was observed. BP 1 is less than 50~o identical to other plant peroxidases which, taken together with its developmentally dependent expression in the endosperm 15-20 days after flowering, suggests a unique biological role of this enzyme. The barley peroxidase is processed at the C-terminus and might be tar