摘要：

1. 1. Hymenolepis incorporates C 14 into organic, keto and amino acids and into polysaccharide when incubated with NaHC 14O 3 and glucose. There is a marked decrease in CO 2 incorporation into polysaccharide under anaerobic conditions. This indicates the presence of an energy-dependent link between the glycotic pathway and the C 4-dicarboxylic acid sequence of the tricarboxylic acid cycle. 2. 2. Phosphoenolpyruvate carboxylase, which serves as this connecting reaction in avian and mammalian tissues, is the most active CO 2-fixing enzyme in Hymenolepis. It is localized mainly in the soluble fraction although some activity is associated with the particulate fractions. There is an increase in this carboxylase activity concomitant with an increase in CO 2 incorporation into polysaccharide. This indicates that the enzyme may also function in this flatworm to convert dicarboxylic acids to phosphopyruvate during gluconeogenesis. 3. 3. Malic acid appears to be the major dicarboxylic acid formed by independent CO 2-fixing reactions in Hymenolepis. Its formation is through the action of a "malic enzyme" and possibly also by a separate reaction. Malate synthesis is localized in the particulate fractions. Pyruvate carboxylase and propionyl-CoA carboxylase activities could not be detected.

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