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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.

1. 1. Hatched second-stage Ascaris larvae have been shown to contain fructose-1,6-diphosphatase and phosphoenolpyruvate carboxykinase, both of which are required for glyconeogenesis which, in turn, is required for the proposed pathway for larval metabolism. 2. 2. In contrast to mammalian skeletal and smooth muscle, adult Ascaris muscle possesses both fructose-1,6-diphosphatase and phosphoenolpyruvate carboxykinase activities. In addition, NaH 14 CO 3 and succinate-2,3- 14 C are incorporated into glycogen when incubated with Ascaris muscle strips. 3. 3. As is the case with the corresponding enzyme from mammalian striated muscle, fructose-1,6-diphophatase preparations from both Ascaris muscle and larvae require Mg 2+ and EDTA for optimal activity, and are inhibited by AMP as well as by high substrate concentrations. 4. 4. Attempts to demonstrate phosphoenolpyruvate carboxykinase activity in the smooth muscle, taenia coli, were negative.

1. 1. Unembryonated Ascris lumbricoides eggs contein a large pool of lipid-bound volatile fatty acids which are released only after saponification of the neutral lipid fraction. Smaller quantities of free volatile acids are also present. 2. 2. Quantitatively, the most significant acids comprising both the pools are α-methylbutyric, α-methylvaleric and acetic. Smaller amounts of propionic, formic, butyric and valeric acids are present. Succinic acid has been found in the free-acid fraction. 3. 3. During embryonation, the concentrations of bound α-methylbutyric and α-methylvaleric acids decrease to very low levels. 4. 4. Low, but significant quantities of C 14 -α-methylbutyriate and C 14 -methylvalerate are incorporated into the corresponding acid of the bound fraction when incubated with the intact reproductive system or cells derived therefrom. 5. 5. Unlike the adult Ascaris muscle, the reproductive tissues do not apper to be capable of synthesizing α-methylbutyrate or α-methylvalerate from acetate plus propionate or two molecules of propionate respectively. 6. 6. C 14 O 2 is fixed rapidly into free succinate and propionate in the egg, and more slowly into bound propionate. C 14 O 2 is also fixed into egg glycogen and trehalose. 7. 7. These findings are consistent with a pathway which can account for the well-established conversion of Ascaris egg lipids into carbohydrates during embryonation without the participation of the glyoxylate cycle. Interrelationships between metabolism of the adult muscle and egg also are discussed.