Carboxydipeptidase from Boophilus microplus: a "concealed" antigen with similarity to angiotensin-converting enzyme.
A protein, Bm91, which was first identified as a protective vaccine antigen from the tick Boophilus microplus, has regions of very strong amino acid sequence similarity to mammalian carboxydipeptidases or angiotensin converting enzymes (ACE; E.C. 3.4.15.1). This protein is now shown to share many biochemical and enzymatic properties with mammalian carboxydipeptidases. It is enzymatically active in a conventional assay for ACE using hippuryl-Gly-Gly as substrate. The hydrolysis of the C-terminal nonapeptide of the insulin B chain proceeds by sequential removal of carboxy-terminal dipeptides. The similarities extend to the dependence of activity on pH and added salt. Bm91 is inhibited by two well-characterized inhibitors of the mammalian enzymes, the drug Captopril and a nonapeptide, and the inhibition occurs in similar concentration ranges to those effective with the mammalian enzymes. However, the natural substrates of the tick enzyme are unknown. Angiotensin I itself is a poor substrate and the enzyme's natural substrates are likely to be one or more of the pharmacologically active peptides occurring in insects and arthropods.
CSIRO Division of Tropical Animal Production, Indooroopilly, Queensland, Australia.
J M
JM
Jarmey
G A
GA
Riding
R D
RD
Pearson
R V
RV
McKenna
P
P
Willadsen
D000595:Amino Acid Sequence; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D004150:Dipeptidases; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000737:chemistry / Q000276:immunology*; D013379:Substrate Specificity; D013987:Ticks / Q000201:enzymology*
C090495:Bm91 protein, Boophilus microplus; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D009842:Oligopeptides; C029275:hippuryl-glycyl-glycine; D002216:Captopril; D004150:Dipeptidases; D007703:Peptidyl-Dipeptidase A