A multi-enzyme cascade of hemoglobin proteolysis in the intestine of blood-feeding hookworms.
Blood-feeding pathogens digest hemoglobin (Hb) as a source of nutrition, but little is known about this process in multicellular parasites. The intestinal brush border membrane of the canine hookworm, Ancylostoma caninum, contains aspartic proteases (APR-1), cysteine proteases (CP-2), and metalloproteases (MEP-1), the first of which is known to digest Hb. We now show that Hb is degraded by a multi-enzyme, synergistic cascade of proteolysis. Recombinant APR-1 and CP-2, but not MEP-1, digested native Hb and denatured globin. MEP-1, however, did cleave globin fragments that had undergone prior digestion by APR-1 and CP-2. Proteolytic cleavage sites within the Hb alpha and beta chains were determined for the three enzymes, identifying a total of 131 cleavage sites. By scanning synthetic combinatorial peptide libraries with each enzyme, we compared the preferred residues cleaved in the libraries with the known cleavage sites within Hb. The semi-ordered pathway of Hb digestion described here is surprisingly similar to that used by Plasmodium to digest Hb and provides a potential mechanism by which these hemoglobinases are efficacious vaccines in animal models of hookworm infection.
Williamson
Angela L
AL
Department of Microbiology and Tropical Medicine, The George Washington University, Washington, DC 20037, USA.
Lecchi
Paolo
P
Turk
Benjamin E
BE
Choe
Youngchool
Y
Hotez
Peter J
PJ
McKerrow
James H
JH
Cantley
Lewis C
LC
Sajid
Mohammed
M
Craik
Charles S
CS
Loukas
Alex
A
D000722:Ancylostoma / Q000033:anatomy & histology / Q000378:metabolism*; D000724:Ancylostomiasis / Q000378:metabolism / Q000469:parasitology; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004285:Dogs; D006454:Hemoglobins / Q000378:metabolism*; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000378:metabolism; D045726:Metalloproteases / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D006454:Hemoglobins; D011994:Recombinant Proteins; D045726:Metalloproteases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D016282:Aspartic Acid Endopeptidases