Carbohydrate digestion in ticks and a digestive α-l-fucosidase

Abstract

Digestive carbohydrases are present in many species of hematophagous Arthropoda, including ticks. In this work, Amblyomma cajennense (Ixodidae) midgut digestive carbohydrases were tracked with different substrates, resulting in the identification of a chitinase and an N-acetyl-β-glucosaminidase and the first description of a digestive α-l-fucosidase in ticks. α-l-fucosidases are involved in various physiological processes, and digestive α-l-fucosidases have been shown to be present in other types of organisms. Amblyomma cajennense α-l-fucosidase activity was isolated using acidic and salting-out precipitations and chromatographic steps in hydrophobic and cation-exchange columns. The specificity of the isolated activity as an α-l-fucosidase was confirmed by the hydrolysis of 4-methylumbelliferyl α-l-fucopyranoside and the natural substrate fucoidan and the inhibition by fucose and deoxyfuconojirimycin. The isolated activity of α-l-fucosidase forms oligomers with molecular mass of 140kDa or 150kDa as determined by gel filtration and non-reducing SDS–PAGE, respectively. This particular fucosidase has an optimum pH of 5.3, is stable even at high temperatures (stable for at least 2h at 50°C), has a Km of 45μM to the substrate 4-methylumbelliferyl α-l-fucopyranoside and IC 50% of 327μM to fucose and 42pM to deoxyfuconojirimycin. The presence of digestive fucosidases in hematophagous Arthropoda may be related to defence mechanisms against host–parasite interactions.