Enzymatic differences between hycanthone-resistant and sensitive strains of Schistosoma mansoni.

1. Hycanthone-sensitive and resistant adult worms of Schistosoma mansoni were found to have generally similar specific activities in ten enzymes of carbohydrate metabolism. 2. Kinetic analyses revealed that pyruvate kinase, glucose-6-phosphate (G6P) dehydrogenase and malate dehydrogenase from both strains possessed similar Michaelis-Menten constants and were not inhibited by hycanthone. 3. Hexokinase and lactate dehydrogenase from the drug-resistant strain were not inhibited by hycanthone and showed three to five times greater Km values than those from the drug-sensitive worms which were also inhibitable by hycanthone. 4. Hycanthone more drastically affected the Vmax of phosphofructokinase from the hycanthone-sensitive parasite. 5. These data showed that the hycanthone inhibitable enzymes were generally from the drug-sensitive strain whereas the enzymes from drug-resistant worms are mostly hycanthone insensitive.