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Endonuclease Activity of Phenol Oxidase From Musca domestica Larvae

¹ Department of Biochemistry and Molecular Biology, China Agricultural University, Beijing 100094, China
² Department of Biochemistry, Hebei Medical University, Shijiazhuang 050017, China

^* To whom correspondence should be addressed. E-mail: weiquan1{at}yahoo.com

Phenol oxidase (PO), a copper-containing enzyme with oxygenase activity, can convert mono- or diphenol into quinone and plays an important role in the arthropod melanization reaction. Here, we report a new property of PO from Musca domestica larvae: a thermotolerant endonuclease activity, by which PO can degrade plasmid DNA even after being heated to 80° C for 20 min. We cloned PO cDNA, constructed the expression vector pVAX1-PO, and expressed it in HeLa cells. The expression product showed the same properties as purified PO. Our data indicate that PO is a bifunctional enzyme, exhibiting both oxygenase and endonuclease activity, suggesting new roles for this important molecule in the innate responses of M. domestica.

Abbreviations: ATA, aurintricarboxylic acid • L-DOPA, L-3,4-dihydroxyphenylalanine • PO, phenol oxidase • proPO, prophenol oxidase • PTU, 1-phenyl-2-thiourea