F. Sezaki et al., Effect of ionic concentration on the higher-order structure of prophenol oxidase in Drosophila melanogaster, BIOCHEM GEN, 39(3-4), 2001, pp. 83-92
Phenol oxidase in Drosophila melanogaster occurs as precursors designated p
rophenol oxidases A(1) and A(3). Crossing experiments between isozyme varia
nts proved that prophenol oxidase in this species is a homodimer Prophenol
oxidases were partially purified using ammonium sulfate fractionation, phen
yl Sepharose, and DEAE-cellulose column chromatography. The preparations we
re mixed, then dialyzed against buffer containing varying salt concentratio
ns. The resulting prophenol oxidase was analyzed by gel electrophoresis. At
20 mM KCl or NaCl, two bands of phenol oxidase were observed, cot-respondi
ng to the parental ones as monomer, whereas at 200 mM KCl or NaCl, three ba
nds appeared in the gel, one being a dimer The monomer-dimer reversibility
of the Drosophila prophenol oxidase depends on the salt concentrations. The
phenol oxidase activity remained unaffected within the KCl concentrations
tested. Considering the ionic concentration of Drosophila hemolymph, these
results indicate that prophenol oxidase exists as a dimer in vivo, and the
higher-order structure of prophenol oxidase can be altered reversibly by io
nic concentrations in vitro.