BIOSYNTHESIS OF CYCLOPROPANE FATTY ACIDS 53 



cells; the incorporation into the resting cells is 9.6%. The 

 mixed fatty acids show little labeling in contrast to other 

 cellular constituents which contain between 98.3 and 99.7% 

 of the radioactivity (Table 2.5). The label present in the 

 mixed fatty acids is distributed in the main between the 

 "dihydroxy" and lactobacillic acid fractions (Table 2.6). 



Samples of biosynthetically labeled lactobacillic acid 

 from the methionine and formate experiments were de- 

 graded in the man jr described, and the specific activity 

 of the resulting ioddlbrm was recorded. As has been men- 

 tioned previously, in this scheme of degradation the iodo- 

 form carbon is derived exclusively from the methylene 

 bridge carbon of the lactobacillic acid molecule. The ob- 

 servation (Table 2.7) that the specific activity of the iodo- 

 form is 84% that of the lactobacillic acid in the methionine 

 experiment and 80% that of lactobacillic acid in the formate 

 experiment demonstrates conclusively that the methylene 

 bridge carbon of the lactobacillic acid molecule is derived 

 from one-carbon fragments. 



OTeary (23, 24) working with L. arahinosus also demon- 

 strated incorporation of c?5-vaccenic acid-l-C^* and of me- 



TABLE 2.7 



Radioactivity of lodoform-C^^ Obtained from 

 Biosynthetic C^^ Lactobacillic Acid 



Methionine- 

 C^^-Formate Methyl-C^^ 



Experiment Experiment 



dis./min./mmole dis./min./mmole 



Lactobacillic acid 3464 22350 



Iodoform 2767 * 18787 * 



* The iodoform was purified to constant radioactivity. 



