Glycosidase activity in the excretory-secretory products of the liver fluke, Fasciola hepatica

Abstract

Fasciola hepatica secretes proteolytic enzymes and other molecules that are essential for host penetration and migration. This mixture may include enzymes required for the degradation of supramucosal gels, which defend epithelial surfaces against pathogen entry. These contain hydrated mucins that are heavily glycosylated. Excretory-secretory products (ES) from F. hepatica were examined for a range of glycosidase activities, using synthetic 4-methylumbelliferyl glycosides as substrates. The ES product contained at least 8 different glycosidase activities, the most abundant of which were beta-N-acetylhexosaminidase, beta-galactosidase and beta-glucosidase. Alpha-fucosidase, beta-glucuronidase, alpha-galactosidase, alpha-mannosidase and neuraminidase were also present. Beta-N-acetylhexosaminidase and beta-galactosidase were present in multiple isoforms (at least 4), whereas beta-glucosidase appeared to exist as one isoenzyme with a pI < 3.8. All three enzymes had acidic pH optima (4.5-5.0). Ovine small intestinal mucin was degraded by ES at pH 4.5 or 7.0, with or without active cathepsin L, the major protease found in F. hepatica ES. The ability of F. hepatica ES to degrade mucin in the presence or absence of active cathepsin L suggests that cathepsin L is not essential for mucin degradation. The abundance of beta-galactosidase and beta-hexosaminidase in ES supports a role for these enzymes in mucin degradation.

Entamoeba histolytica cysteine proteases cleave the MUC2 mucin in its C-terminal domain and dissolve the protective colonic mucus gel

“…After successful colonization on the mucus layer of the gastrointestinal tract, invading bacteria, viruses, or parasites must overcome the mucus barrier. Virulence factors such as proteases, glycosidases, and mucus secretagogues are produced by these organisms and are believed to be responsible for disruption and depletion of the mucus gel (9)(10)(11)(12). E.h. constitutively secretes at least four cysteine proteases that are involved in tissue destruction and invasive disease (22,23).…”

“…Microbes accomplish this task by a variety of mechanisms, including degradation of mucin oligosaccharides, proteolytic degradation of the mucin polymer, and induction of mucus hypersecretion (9)(10)(11)(12). The protozoan parasite Entamoeba histolytica (E.h.) colonizes the mucus layer of the colon by adhering to mucin oligosaccharides by means of a 170-kDa Gal͞GalNAc-lectin (13).…”

Activity of selected hydrolytic enzymes from leeches (Clitellata: Hirudinida) with different feeding strategies

“…They perform many functions -they decompose the tissue barrier, inhibit the process of host blood coagulation and defend the parasite from the response of the host's immunological system. Activities of eight different glucosidases (α-galactosidase, β-galactosidase, β-glucuronidase, β-glucosidase, β-Nacetyl-hexosaminidase, α-mannosidase, α-fucosidase, neuraminidase) were found in the ES products of F. hepatica, apart from proteases (Irwin et al 2004). These enzymes digest glucoproteins, thereby enabling the parasite to penetrate a host epithelium.…”

“…They are produced by cells situated in the oesophagus or by secretive glands and are referred to as excretive-secretive products (ES). The composition of the products has been particularly well-studied in Platyhelminthes and Nematoda (Ruitenberg & Loendersloot 1971;Hinck & Ivey 1976;Matthews 1984;Knox & Kennedy 1998;Moczoń & Wranicz 1999;Jefferies et al 2001;Irwin et al 2004). The enzymes contained in ES products (phosphatases, aminopeptydases, oxidoreductases, esterases, glucosidases) are referred to as penetrating enzymes.…”

“…In the present study, high aminopeptidase and glucosidase activities along with high activities of phosphatases and esterases were detected in the head segment of parasitic leeches. These are enzymes which, in other parasites (Hinck & Ivey 1976;Knox & Kennedy 1998;Irwin et al 2004), take part in digesting the tissue barrier, thereby enabling penetration into the host body and moving inside it. In parasitic leeches, these enzymes may take part in digesting the tissue barrier and facilitate the penetration of the host body to reach its blood vessels and sub-sequent food intake.…”