no BIOLOGICAL CHEMISTRY 



yO O y OH I/O 



CH 3 C< +CH 3 Cf ->CH 3 -C<_CH 2 C( -> 

 H \H \ H VH 



CH 3 CH 2 'CH 2 -<;OOH 



Three or four molecules of acetaldehyde give fatty acids with 

 six or eight carbon atoms respectively, and so upwards to the 

 higher fatty acids. 



Another hypothesis for the formation of fatty acids is 

 that of Smedley, who pointed out that pyruvic acid is decom- 

 posed to form acetaldehyde, which condenses with pyruvic 

 acid to form an hydroxylated acid. This acid is converted 

 into an unsaturated acid, and then reduced to a saturated 

 acid. Removal of carbon dioxide from the above un- 

 saturated acid gives an aldehyde with four carbon atoms 

 which can condense with a further molecule of pyruvic acid. 



(1) CH 3 CO COOH -> CH 3 CHO + CO 2 



Pyruvic acid Acetaldehyde 



(2) CH 3 CHO + CH 3 COCOOH = CH 3 CHOH CH 2 COCOOH 



CH 3 CH : CHCOCOpH 



Pentylinic a-keto-acid. 



(3) CH 3 CH : CHCO-COOH -f O = CH 3 CH : CH'COOH 

 (40) CH 3 CH : CHCOOH + 2H = CH 3 CH 2 CH 2 COOH 



Butyric Acid 



(36) CH 3 CH : CHCOCOOH = CH 3 CH : CH-CHO + CO 2 



Pentylenic d-keto-acid. Compare with reaction (i.) 



(4&)CH 3 -CH : CHCHO + C 3 COCOOH = 



(Compare with reaction 2.) 



CH 3 CH : CHOH.CH 2 COCOOH 



and by reactions similar to (30) and (40) Caproic Acid 

 CH 3 CH 2 CH 2 CH 2 CH 2 COOHis formed, reduction taking place 

 as a final step. * 



Some such method of synthesis is extremely probable 

 as pyruvic acid is formed in the body. It should be noted 

 that the steps of synthesis do not correspond to those of 

 oxidation, but if the compound on the right of equation (2) 

 were oxidised as in (30), and then water added, we would 

 have CH 3 CHOHCH 2 COOH, or jff-hydroxybutyric acid from 

 which the other "acetone " bodies can be formed. 



METABOLISM OF PROTEINS 



The oxidation of proteins can be treated as the oxidation 

 of their constituent amino acids. The first stage is the 



* I. Smedley and E. Lubrzynska, Biochem. Journ., 1913, vol. 7, 

 p. 364. 



