Antibacterial peptides from various sources express different antibacterial activity. In order to obtain a high activity antibacterial peptide, the sequences of four antimicrobial peptides-Protegrin-1, 4 kDa Scorpion Defensin, Metalnikowin-2A and Sheep Myeloid Antibacterial Peptide SMAP-29-were exploited to generate a synthetic antimicrobial peptide cp gene, which was then cloned into the expression vector pPICZ alpha-A. The constructed recombinant expression vector pPICZ alpha-cp was transformed into Pichia pastoris X-33, in which the synthetic antimicrobial peptide (CP) could be expressed under the control of the inducible AOX1 promoter and secreted via the a mating factor leader of Saccharomyces cerevisiae. Results showed that recombinant plasmid is highly stable, and In vitro experiments showed that the recombinant antimicrobial peptide CP is heat and acid-stable, and it has high antibacterial activity against several Gram-positive and -negative bacteria. Only 1 mu g of the recombinant antimicrobial peptide CP has an antibacterial activity equivalent to 64 U ampicillin. Thus, this recombinant antimicrobial peptide could serve as an attractive candidate for the development of therapeutic antimicrobial drugs. (c) 2007 Published by Elsevier Inc.