FUNCTIONS OF PHOSPHOENOLPYRUVATE CARBOXYKINASE AND MALIC ENZYME IN ANAEROBIC FORMATION OF SUCCINATE BY ASCARIS LUMBRICOIDES

1. 1. Carbon dioxide stimulates two- to threefold the formation of pyruvate from phosphoenolpyruvate (PEP), and lactate from fructose-1,6-diphosphate by Ascaris muscle homogenates. 2. 2. The apparent Km value of Ascaris PEP carboxykinase for PEP is approximately one-seventh that for oxalacetate, which may account partially for the enzyme acting in a direction opposite to that reported for mammalian tissues. 3. 3. Distribution of enzymes and balance studies of malate utilization by Ascaris mitochondria suggest that cytoplasmic malate enters the mitochondrion, whereupon half is oxidized via the malic enzyme to pyruvate and acetate, while the remainder is reduced to succinate and propionate with the generation of ATP. © 1969.