Rh. Fetterer et Ml. Rhoads, Characterization of acid phosphatase and phosphorylcholine hydrolase in adult Haemonchus contortus, J PARASITOL, 86(1), 2000, pp. 1-6
An acid phosphatase (AP) and a phosphorylcholine hydrolase (PCH) were detec
ted in excretory-secretory (ESP) products from adult Haemonchus contortus.
The AP had a pH optimum of 4.5 and was inhibited by tartaric acid and sodiu
m fluoride. but not by o-phenanthroline. The AP hydrolyzed paranitrophenol
(pnp)-phosphate and to a lesser extent pnp-phenyl-phosphonate but did not h
ydrolyze diester substrates. Purified AP consisted of heterodimers with rel
ative molecular weight (Mr) of 41.9 and 48.7 kDa and had a native molecular
weight of 98 kDa by size-exclusion chromatography (SEC). The PCH had a FH
optimum of about 9.5 and was inhibited by EDTA and o-phenanthroline but not
by the specific phospholipase inhibitor D609. The specific activity of PCH
in the ESP was aproximately 25-fold less than that of AP. PCH also hydroly
zed 5'-thymidine monophosphate-pnp at a rate about 40% lower than pnp-phosp
horylcholine but did not hydrolyze 3'-thymidine monophosphate-pnp. Pal tial
purification of PCH suggests an Mr of 50.2 kDa by sodium dodecyl sulfate-p
olyacrylamide gel electrophoresis and an Mr of 102 kDa by SEC. Both AP and
PHC were secreted in vitro in a time-dependent manner and had their highest
concentrations in the intestine. The results indicate that H. contortus ad
ults secrete significant amounts of AP that might be a digestive enzyme. PC
H is also an intestinal enzyme and is secreted in lesser amounts than AP. T
he PCH is probably not a phospholipase C but has some characteristics of a
type I phosphodiesterase.