A Protein Factor Inhibiting Activation of Prophenoloxidase with Natural Activator and Its Purification

Abstract

Fractionation of the crude prophenoloxidase solution from prepupae of housefly, Musca domestica vicina Maquart, was carried out. The soluble fraction of 40% saturation of am-monium sulfate contained a certain factor being able to inhibit the activation of prophe-noloxidase A with natural activator from aged pupae. The factor seemed to be a protein and was named Factor N tentatively.
Purification of Factor N by gel filtration on Sephadex G-75 and sucrose density gradient ultracentrifugation resulted in an 18.2% of the yield of the activity and a 21.8-fold increase in the specific activity. The purified preparation of Fractor N had a sedimentation constant of 5.4 S.