Hyaluronidase isoforms from developing embryos of the camel tick Hyalomma dromedarii

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

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 140 kDa or 150 kDa 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 45 μM to the substrate 4-methylumbelliferyl α-L-fucopyranoside and IC 50% of 327 μM to fucose and 42 pM to deoxyfuconojirimycin. The presence of digestive fucosidases in hematophagous Arthropoda may be related to defence mechanisms against host-parasite interactions.

Kinetic analysis of hyaluronidase activity using a bioactive MRI contrast agent

One of the attractions of molecular imaging using 'smart' bioactive contrast agents is the ability to provide non-invasive data on the spatial and temporal changes in the distribution and expression patterns of specific enzymes. The tools developed for that aim could potentially also be developed for functional imaging of enzyme activity itself, through quantitative analysis of the rapid dynamics of enzymatic conversion of these contrast agents. High molecular weight hyaluronan, the natural substrate of hyaluronidase, is a major antiangiogenic constituent of the extracellular matrix. Degradation by hyaluronidase yields low molecular weight fragments, which are proangiogenic. A novel contrast material, HA-GdDTPA-beads, was designed to provide a substrate analog of hyaluronidase in which relaxivity changes are induced by enzymatic degradation. We show here a first-order kinetic analysis of the time-dependent increase in R(2) as a result of hyaluronidase activity. The changes in R(2) and the measured relaxivity of intact HA-GdDTPA-beads (r(2B)) and HA-GdDTPA fragments (r(2D)) were utilized for derivation of the temporal drop in concentration of GdDTPA in HA-GdDTPA-beads as the consequence of the release of HA-GdDTPA fragments. The rate of dissociation of HA-GdDTPA from the beads showed typical bell-shaped temperature dependence between 7 and 36 degrees C with peak activity at 25 degrees C. The tools developed here for quantitative dynamic analysis of hyaluronidase activity by MRI would allow the use of activation of HA-GdDTPA-beads for the determination of the role of hyaluronidase in altering the angiogenic microenvironment of tumor micro metastases.