Hyal are also present in almost all venoms, acting as

a “diffusion factor” by facilitating the penetration of the other harmful venom components and enhancing their action in various tissues into the bloodstream (Kemparaju and Girish, find more 2006; Senff-Ribeiro et al., 2008). Hyal have been described as “allergenic factors” in scorpion, bee, and wasp venoms, and are able to induce severe and fatal anaphylactic IgE-mediated reactions in humans (Lu et al., 1995; Kolarich et al., 2005). Hyal have already been characterized as glycoproteins (Kemeny et al., 1984; Jin et al., 2008) and analysis by high performance liquid chromatography and mass spectrometry revealed that the α-1,3-fucose-containing N-glycan is the fundamental structure responsible for their allergenicity (Kubelka Selleck XL184 et al., 1995; Kolarich and Altmann, 2000; Kolarich et al., 2005). Since allergenic Hyal are phylogenetically more

conserved among the other Hymenoptera allergens (e.g. Ag5 and PLA1), a significant degree of homology is observed among the sequences and 3D structures of these proteins, whether they are from different vespids or honeybee Apis mellifera venom (Api m 2) ( Jin et al., 2010). In addition, a large percentage of patients allergic to Hymenoptera venom show reactivity to both bee and wasp venoms (known as cross-reactivity) in tests for the presence of IgE-specific antibodies ( Hemmer, 2008). This makes selection of the most suitable venom for immunotherapy difficult. However, it is unclear whether this cross-reactivity is due to (a) sequence homology between these hyaluronidases; (b) sensitivity to the specific IgE antibodies; or (c) cross-reactive N-glycans (cross-reactive carbohydrate determinants [CCDs]), which have been investigated unless in allergens from different sources ( Jin et al., 2010; Eberlein et al., 2012; Al-Ghouleh et al.,

2012). In terms of the mechanism of action on the substrate, Hyal enzymes are classified into three types (Meyer, 1971): (a) the group of the endo-β-N-acetyl-d-hexosaminidases that hydrolize the high molecular weight substrate (HA) to tetrasaccharide as the main end product, being this group represented by the testicular enzyme; (b) the β-endoglucuronidases group represented by hyase from leeches and hookworm ( Hotez et al., 1994); (c) and finally the group of lyases that act via β-elimination, yielding disaccharides as the main end products represented by the bacterial hyases. According to Laurent (1989), Cramer et al. (1994) and Takagaki et al. (1994) the enzymes of the first group also catalyzes transglycosylation reactions, producing hexa-, di-, and octa-saccharides during hydrolysis of HA. Hyaluronate-4-glycanohydrolase (EC 3.2.1.35), or Hyal type 1, is an endo-β-N-acetyl-d-hexosaminidase is also found in Hymenoptera venoms and mammalian spermatozoa.