CFD, also known as Complement factor D preproprotein, is a serine protease that stimulates glucose transport for triglyceride accumulation in fats cells and inhibits lipolysis. There are two antiparallel beta-barrel domains with each barrel containing six beta-strands with the same typology in all enzymes. The major difference in backbone structure between Factor D and the other serine proteases of the chymotrpsin family is in the surface loops connecting the secondary structural elements. Factor D displays different conformations of major catalytic and substrate-binding residues typically found in the chrotrypsin family. Recombinant human CFD, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.