Recombinant Drosophila prophenoloxidase 1 is sequentially cleaved by alpha-chymotrypsin during in vitro activation
2014 (English)In: Biochimie, ISSN 0300-9084, E-ISSN 1638-6183, Vol. 102C, 154-165 p.Article in journal (Refereed) Published
Insect prophenoloxidase (PPO) is an essential innate immunity protein to induce pathogen into melanization. In Bombyx mori, pro-phenoloxidase-activating enzyme (PPAE) can directly cleave and activate PPO. However, PPO in Manduca sexta cannot be cleaved into active phenoloxidase (PO) by serine proteases unless cofactors are involved, which indicates that PPO activation is complicated. Here we use recombinant Drosophila melanogaster prophenoloxidase 1 (rPPO1) to study the mechanism of PPO activation induced by a typical serine protease, alpha-chymotrypsin. Small amounts of alpha-chymotrypsin cleave rPPO1 at the N- and C-terminus to produce a large fragment rPPO1(N1/C1) that needs further cleavage by alpha-chymotrypsin to produce a smaller fragment rPO1(60-kD) with PO activity. rPO1(60-kD) oxidizes dopamine without being affected by high temperature, or by having salt and Ethylene diamine tetraacetic acid (EDTA) in the solution. After incubation with dopamine, rPO1(60-kD) cannot be detected using reducing SDS-PAGE due to formation of a large complex. Trypsin, another typical serine protease, cleaves rPPO1 at the N- and C-terminus to produce a small fragment rPPO1(N'/C') without PO activity. Several rPPO1 mutants were created through over-expressing active fragments that have direct PO activity. They are easily cleaved by low amounts of alpha-chymotrypsin without increasing PO activity. Therefore, rPPO1 can be sequentially cleaved in at least three places by alpha-chymotrypsin to produce activated rPO1(60-kD).
Place, publisher, year, edition, pages
2014. Vol. 102C, 154-165 p.
Prophenoloxidase, Structure, Immunity, alpha-chymotrypsin
IdentifiersURN: urn:nbn:se:uu:diva-229722DOI: 10.1016/j.biochi.2014.03.007ISI: 000338623600018OAI: oai:DiVA.org:uu-229722DiVA: diva2:738467