Characterisation of aminopeptidase activity in scab mites, Psoroptes spp.

Soluble and membrane-bound aminopeptidase activities were demonstrated in extracts of P. cuniculi (Delafond). Leucine amino-peptidase (LAP) activity in the soluble fraction of P. cuniculi extracts displayed substrate preference for amino acid derivatives with terminal leucine and methionine over those with acidic, basic or heterocyclic groups. P. cuniculi LAP was inhibited by leucinethiol (IC50 = 1.4 +/- 0.4 nM), bestatin (IC50 = 3.9 +/- 1.7 muM), Arphamenine A (IC50 = 0.37 +/- 0.03 mM) the chelating agent 1,10-phenanthroline (IC50 = 2.3 +/- 0.5 mM), Zn2+, Cu2+ Ni2+, and Co2+, and activated by Mn2+ and Mg2+. The LAP activity was visualised as a single major band after electrophoresis on native gels and eluted from a size exclusion column as a single major peak representing a molecular mass range of 85-116 kDa.

Degenerate oligonucleotide primers were used to amplify short fragments of genomic DNA containing nucleotide sequence coding for the cation-binding motifs of the co-catalytic Zn2+ binding domains of dizinc leucine aminopeptidases in both P. cuniculi and P.ovis (Hering). The major soluble aminopeptidase from these mites therefore displays most of the characteristics associated with typical cytosolic leucine aminopeptidases belonging to the M17 family of metalloproteinases. (C) 2002 Elsevier Science Ltd. All rights reserved.