<span style="font-size:14.0pt;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:AR-SA">Purification and characterization of a cholinesterase from <i>Haemonchus contortus</i></span>

Abstract

Acetylcho<span style="font-size:14.0pt; font-family:HiddenHorzOCR;mso-bidi-font-family:HiddenHorzOCR">linesterase (AChE) was purified from the extract of adult <i>Haemonchus contortus</i> &nbsp;by gel filtration, ion-exchange and ConA-Sepharose chromatography. The enzyme was also found to be secreted by the parasite during <i>in </i><i>vitro </i>cultivation which was partially purified from the excretory-secretory products. Presence of enzyme specific antibodies were observed in animals having <i>H. contortus</i><i> </i>infection. The molecular mass of the enzyme by SDS-PAGE was 144 kDa. The enzyme showed typical Michaelis-Menten kinetics at low substrate concentrations but was inhibited by substrate

concentrations greater than 4 <i>mM. </i>The enzyme was stab le at 4°C for several weeks but lost 60% of the activity when heated to 60°C for 5 min. Physostigmine and neostigmine inhibited enzyme activity at low <span style="font-size:14.0pt;font-family:HiddenHorzOCR;mso-bidi-font-family:HiddenHorzOCR">( μ<span style="font-size:14.0pt;font-family:HiddenHorzOCR;mso-bidi-font-family:HiddenHorzOCR">M) concentrations whereas phenyl methyl sulfonyl fluoride (PMSF) and sodium fluoride (NaF) inhibited only at high concentrations <i>(mM) . </i>Significance of

secreted AChE in host-parasite relationship is discussed.

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