PARTIAL-PURIFICATION AND COMPARISON OF THE KINETIC-PROPERTIES OF OVINE LIVER ECHINOCOCCUS-GRANULOSUS HYDATID CYST FLUID MALATE-DEHYDROGENASE AND THE CYTOPLASMIC ENZYME FROM THE HOST LIVER

Ovine liver Echinococcus guanulosus hydatid cyst fluid and cytoplasmic healthy ovine liver malate dehydrogenases were purified 24- and 30-fo ld by Sephadex G-200 and DEAE-Sephadex chromatography. Both enzymes we re eluted with the same elution volume and the same salt concentration from the respective columns. The pH optimum of the enzymes from both sources was 8.4 in either Tris-HCl or barbital buffer. The K-m values for oxaloacetate were 0.211 and 0.200 mM for hydatid cyst fluid and he althy ovine liver enzymes, respectively. The K-m values for NADH were 0.220 and 0.213 mM for hydatid cyst fluid and healthy ovine liver enzy mes, respectively. Enzyme from both sources demonstrated similar heat denaturation patterns. Both enzyme preparations were inhibited at high concentrations of either substrate. Neither enzyme was inhibited by p ara-hydroxymercuribenzoate or fumarate, and both enzyme preparations w ere specific for NADH as a cofactor. The results are discussed in term s of the possible infiltration of the host enzyme into the cyst fluid.