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.
Jarmey
J M
JM
CSIRO Division of Tropical Animal Production, Indooroopilly, Queensland, Australia.
Riding
G A
GA
Pearson
R D
RD
McKenna
R V
RV
Willadsen
P
P
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