Salivary gland sporozoites of the malaria parasite Plasmodium express a major surface coat protein, CSP. The N-terminus of this protein is hypothesized to be enzymatically processed, revealing a Gln residue which is then enzymatically converted pyro-Glu. We analyzed P. falciparum salivary gland sporozoites, recombinant PfCSP, and synthetic peptides in order to characterize this cleavage site and its conversion.