The Mechanism of the Formation of α-Methylbutyrate from Carbohydrate by Ascaris lumbricoides Muscle

SUMMARY 1. Muscle strips from the helminth Ascaris Zumbricoides in- corporate acetate-l-Cl4 and acetate-2-Cl4 into ar-methylbutyrate. Isotope from acetate-l-Cl4 and acetate-2-Cl4 are incorporated into carbons 3 and 4 respectively of cr-methylbutyrate. 2. Ascaris muscle strips also incorporate propionate-1-U4, propionate-2-Cl4 and propionate-3-Cl4 into cw-methylbutyrate. Isotope from these species of propionate are incorporated into carbons 1, 2, and 5, respectively, of cr-methylbutyrate. 3. The degree of incorporation of isotopic acetate and pro- pionate into a-methylbutyrate, as well as the distribution of labeling found, indicate that the branched chain carbon skeleton of a-methylbutyrate is formed by a condensation of the acetate carboxyl carbon with carbon 2 of propionate. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. REFERENCES BUEDING, E., Physiol. Revs., 29, 195 (1949). BUEDING, E., AND CHARMS, B., J. Biol. Chem., 196,615 (1952). SAZ,