Efficient production of casoxin D, a bradykinin agonist peptide derived from human casein, by Bacillus brevis

We efficiently produced a small peptide by the host-vector system using Bacillus brevis as a host. DNA encoding the physiologically functional casoxin D, composed of seven amino acids, was ligated in tandem. An expression-secretion vector containing DNA, which codes for a fusion protein of epidermal growth factor-casoxin D pentamer, was constructed. B. brevis transformed with this plasmid produced about 0.5 g/liter of the fusion protein in the culture supernatant. The fusion protein was purified with ammonium sulfate fractionation from the supernatant and digested with two kinds of proteinases. A peptide well separated by high pressure liquid chromatography was identified as biologically active casoxin D.