Cysteine proteases as digestive enzymes in parasitic helminths

• Published in: PLoS neglected tropical diseases 2018-08, Vol.12 (8), p.e0005840-e0005840
• Main Authors: Caffrey, Conor R, Goupil, Louise, Rebello, Karina M, Dalton, John P, Smith, David
• Format: Article
• Language: English
• Subjects: Anatomical structures; Animals; Aquatic invertebrates; Biology and Life Sciences; Cathepsins; Chemotherapy; Cloning; Cysteine; Cysteine Proteases - metabolism; Digestion - physiology; Digestive enzymes; Digestive system; Digestive tract; Disease control; Enzymatic activity; Enzyme activity; Enzymes; Gastrointestinal tract; Helminths; Helminths - enzymology; Helminths - metabolism; Hemoglobin; Medicine and Health Sciences; Migration; Nematodes; Nutrients; Nutrition; Organic chemistry; Parasites; Parasites - enzymology; Parasites - metabolism; Proteases; Proteins; Research and Analysis Methods; Review; Substrates; Tissue; Tissues; Tropical diseases; Vaccines
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0005840

We briefly review cysteine proteases (orthologs of mammalian cathepsins B, L, F, and C) that are expressed in flatworm and nematode parasites. Emphasis is placed on enzyme activities that have been functionally characterized, are associated with the parasite gut, and putatively contribute to degrading host proteins to absorbable nutrients [1-4]. Often, gut proteases are expressed as multigene families, as is the case with Fasciola [5] and Haemonchus [6], presumably expanding the range of substrates that can be degraded, not least during parasite migration through host tissues [5]. The application of the free-living planarian and Caenorhabditis elegans as investigative models for parasite cysteine proteases is discussed. Finally, because of their central nutritive contribution, targeting the component gut proteases with small-molecule chemical inhibitors and understanding their utility as vaccine candidates are active areas of research [7].