Proteolytic activity of Boophilus microplus Yolk pro-Cathepsin D (BYC) is coincident with cortical acidification during embryogenesis.
In a previous report (Parasitology 116 (1998) 525) we isolated and characterized Boophilus Yolk pro-Cathepsin (BYC), an aspartic proteinase precursor from the eggs of the hard tick. The present study was designed to characterize the function of BYC in the consumption of vitellin (VT), the major yolk protein, during embryogenesis. Both purified BYC and total egg homogenate proteolytic activity showed a similar pH dependence profile with an acidic optimum. Purified BYC presented higher activity against VT as a substrate when compared to other proteins. The VT degradation pattern observed in vitro also showed a similar profile to that observed in vivo. Co-localization of BYC and acidic cortical yolk granules was performed by immunocytochemistry and confocal microscopy. Proton-pumping activity of yolk granules in vitro was higher in eggs collected 4 day after oviposition than in newly laid eggs. Taken together, our data suggest that BYC plays a major role in the degradation of VT and that its activity is controlled by acidification of yolk platelets localized at the cortical cytoplasm of the developing Boophilus microplus egg.
Abreu
Leonardo A
LA
Laboratório de Química e Função de Proteinas e Peptideos, CBB-UENF, Avenida Alberto Lamego 2000, Horto, Campos dos Goytacazes, Rio de Janeiro, CEP 28015-620 Brazil.
Valle
Denise
D
Manso
Pedro P A
PP
Façanha
Arnoldo R
AR
Pelajo-Machado
Marcelo
M
Masuda
Hatisaburo
H
Masuda
Aoi
A
Vaz
Itabajara
I
Lenzi
Henrique
H
Oliveira
Pedro L
PL
Logullo
Carlos
C
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004527:Egg Proteins / Q000378:metabolism; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007120:Immunochemistry; D026863:Ixodidae / Q000196:embryology* / Q000201:enzymology*; D018613:Microscopy, Confocal; D010063:Ovum / Q000201:enzymology* / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity
D004527:Egg Proteins; D004792:Enzyme Precursors; D016282:Aspartic Acid Endopeptidases; C113293:Boophilus yolk pro-cathepsin; D006180:Proton-Translocating ATPases