Ascorbate peroxidase: A novel antioxidant enzyme in insects

✍ Scribed by M. Claravon Mathews; Clinton B. Summers; Gary W. Felton

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 81 KB
• Volume: 34
• Category: Article
• ISSN: 0739-4462
• DOI: 10.1002/(sici)1520-6327(1997)34:1<57::aid-arch5>3.0.co;2-t

✦ Synopsis

Ascorbate peroxidase (APOX) activity, which catalyzes the oxidation of ascorbic acid with the concurrent reduction of hydrogen peroxide (H 2 O 2 ), was found in larvae of Helicoverpa zea. Since insects apparently lack a Se-dependent glutathione peroxidase and since catalase has a low affinity for H 2 O 2 , this enzyme may be important in removing H 2 O 2 in insects. We partially purified the APOX activity 58× from the whole body homogenates and investigated its activity with model lipid peroxides, electron donors, and known inhibitors of plant APOX.

The H. zea APOX has activity with model lipid peroxides. This, along with the APOX activity found in fat body tissues, suggests that ascorbate peroxidase may be important in removing lipid peroxides in insects. The H. zea APOX has broader specificity for electron donors than the plant APOX with activity using cysteine, NADPH, glutathione, and cytochrome C as electron donors (22-93% of activity with ascorbate). The H. zea APOX is also resistant to many of the known inhibitors of plant APOX, suggesting that the enzyme has a different active site and may not be a heme-peroxidase.