RESUMEN

A low molecular mass monomeric protein termed Fh-KTM (Fasciola hepatica Kunitz-type molecule) was isolated from the trematode Fasciola hepatica. Fh-KTM is a single polypeptide of 58 amino acids and a Mr of 6751. The complete amino acid sequence of Fh-KTM was determined and revealed significant similarity to the Kunitz-type (BPTI) family of proteinase inhibitors. Several polymorphisms were observed suggesting that more than one Fh-KTM molecule may be expressed by this parasite. Modified proline residues were shown to occur at all four positions in this protein as 3-hydroxy derivatives. This is the first report of 3-hydroxyproline residues in a Kunitz-type molecule. Indirect immunofluorescence and immunogold labelling revealed that Fh-KTM is an abundant molecule within the parasite localised to the gut, the parenchymal tissue and the tegument of adult F. hepatica. Serine protease inhibition assays revealed that Fh-KTM exhibited little or no inhibition against chymotrypsin, kallikrein, urokinase or key serine proteases of the blood coagulation pathways. However, Fh-KTM was able to inhibit trypsin even though the P1 reactive amino acid of Fh-KTM was a leucine residue.

Asunto(s)

Fasciola hepatica/genética , Proteínas del Helminto/genética , Secuencia de Aminoácidos , Animales , Aprotinina/química , Aprotinina/genética , Aprotinina/aislamiento & purificación , Fasciola hepatica/química , Proteínas del Helminto/química , Proteínas del Helminto/aislamiento & purificación , Inmunohistoquímica , Datos de Secuencia Molecular , Peso Molecular , Homología de Secuencia de Aminoácido , Inhibidores de Serina Proteinasa/química , Inhibidores de Serina Proteinasa/genética , Inhibidores de Serina Proteinasa/aislamiento & purificación , Inhibidores de Tripsina/química , Inhibidores de Tripsina/genética