Analysis of two incompletely spliced Arabidopsis cDNAs encoding novel types of peroxidase

Most known class III peroxidase genes contain three introns at conserved positions. Two Arabidopsis cDNAs (ESTs), encoding novel type peroxidases ATP9a and ATP15a were sequenced, and found to contain inserts for intron 2. PCR and sequence analysis of genomic DNA revealed that the atp9a gene contains all three introns, whereas atp15a contains only introns 2 and 3. The ATP15a cDNA intron contained a single base substitution reducing the splicing potential significantly as compared with the genomic sequence. The putative enzymes share essential catalytic and structural features with horseradish peroxidase, despite a pair-wise sequence identity of only 40-45% among the three.