Ml. Rhoads et al., SECRETION OF AN AMINOPEPTIDASE DURING TRANSITION OF 3RD-STAGE TO 4TH-STAGE LARVAE OF ASCARIS-SUUM, The Journal of parasitology, 83(5), 1997, pp. 780-784
Protease activity was identified in culture fluids collected during in
vitro development of L3 to L4 larval stages of Ascaris suum. Fluoroge
nic peptide substrates with unblocked N-termini were specifically hydr
olyzed indicating aminopeptidase activity; a terminal arginyl residue
was preferred, Culture fluids did not hydrolyze fluorogenic peptide su
bstrates with blocked N-termini (endopeptidase substrates). The aminop
eptidase activity was inhibited by 1,10-phenanthroline (metalloproteas
e inhibitor) and by amastatin and bestatin (aminopeptidase inhibitors)
; AEBSF (serine protease inhibitor), Z-pbe-ala-FMK and E-64 (cysteine
protease inhibitors), and pepstatin A (aspartyl protease inhibitor) ha
d little effect on activity. The apparent molecular weight of the amin
opeptidase was estimated gy sucrose density gradient centrifugation at
293 kDa. The aminopeptidase displayed an acidic isoelectric point of
4.7. The peak secretion of the aminopeptidase was temporally associate
d with molting and suggests a function for the protease in this comple
x process.