title: A cysteine endopeptidase from tick (Rhipicephalus (Boophilus) microplus) larvae with vitellin digestion activity.
abstract: The hard tick Rhipicephalus (Boophilus) microplus is a blood-sucking ectoparasite. R. microplus free-living stage comprises egg development, hatching, and subsequent larval development until encountering a host. In order to complete the embryological development, this tick relies on yolk reserve substances, mainly vitellin (Vt), which is still present in the larval stage. The present study demonstrates presence and digestion of Vt in unfed R. microplus larvae. An increasing proteolytic activity is observed in larval development, as well as a decrease in total protein and in Vt content. Partial purification and characterization of a R. microplus larval cysteine endopeptidase (RmLCE) with Vt-degrading activity is also described. RmLCE has optimal activity at 37 degrees C at pH 5.0, being unstable at pH > or =7.5. This enzyme is active upon fluorogenic peptide substrates and is able to degrade Vt, its putative natural substrate. These results indicate that RmLCE has a role in supporting the nutritional needs of unfed R. microplus larva through Vt proteolysis, allowing survival until the first blood meal.
authors.affiliation: Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Andréia
authors.initials: A
authors.lastname: Estrela
authors.forename: Adriana
authors.initials: A
authors.lastname: Seixas
authors.forename: Carlos
authors.initials: C
authors.lastname: Termignoni
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003545:Cysteine / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000302:isolation & purification* / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007814:Larva / Q000201:enzymology*; D048494:Rhipicephalus / Q000201:enzymology* / Q000254:growth & development* / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature; D047048:Vitellins / Q000378:metabolism*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D005456:Fluorescent Dyes; D047048:Vitellins; D003546:Cysteine Endopeptidases; D003545:Cysteine