Immunoscreening an Ancylostoma caninum cDNA library with canine hookworm-infected dog serum resulted in the isolation of a 461 bp cDNA encoding Ac-AP-12, a new 9.1 kDa anticoagulant peptide (100 amino acids) with 43-69% amino acid homology to other nematode anticoagulant peptides (NAPs) from Ancylostoma hookworms. Messenger RNA transcription and expression of Ac-AP-12 was unique to the adult stage of A. caninum. The yeast expressed recombinant Ac-AP-12 demonstrated potent anticoagulant activity on human blood plasma in a concentration dependent manner, and was shown to specifically inhibit human factor Xa activity. Immunolocalization with specific rabbit antiserum showed that Ac-AP-12 was exclusively located in the esophageal glands of adult hookworm. Ac-AP-12 is hypothesized to facilitate both parasite blood feeding and digestion.
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