Abstract
In Euglena, which lacks catalase, ascorbate peroxidase (APX) is the major H2O2-scavenging enzyme. In the present study, to clarify the molecular aspects of the Euglena APX, we have isolated a full-length cDNA clone for the enzyme. The full-length cDNA was cloned by PCR based on the Euglena EST database. Interestingly, the primary structure of the enzyme showed that the enzyme consists of two homologous catalytic domains and 102 amino acids extension at the N-terminal region, which has a typical class II signal for plastid targeting in Euglena. A computer-assisted structure analysis indicated that the enzyme forms an intermolecular dimmer structure. By the cell fractionation analysis, the APX protein had determined in only cytosol fraction, but not in plastid fraction, indicating that Euglena APX became the mature form in cytosol after processing of the precursor.
