Pfizer Handbook of Microbial Metabolites 52 



methylated acids the oxygen and methyl groups usually appear 

 in positions consistent with the acetate theory of fatty acid 

 biogenesis. These bacteria seem to be able also (in effect) to 

 couple two long chain fatty acids to form ketones and branched 

 chain acids. 



Bacterial lipopolysaccharides are irritating pyrogens, relatively 

 toxic to higher animals. The polysaccharide component is the 

 carrier of serological effects, while the lipide moiety has an 

 affinity for the surface of erythrocytes and produces the toxic 

 and pyrogenic effect.^- The high molecular weight wax called 

 cord factor from mycobacteria is quite toxic (quantitatively 

 comparable to diphtheria toxin) and is believed by some to be 

 the principal factor responsible for the virulence of tuberculosis 

 pathogens. Some of the simpler liposaccharides are shown in 

 this section. References to those of higher molecular weight 

 are included in an appendix. 



Phosphatides are widely distributed in nature, though gen- 

 erally in small quantities. They are difficult to handle intact, 

 and few have been well characterized. The metabolism, theories 

 of function and biosynthesis of phospholipides have been re- 

 viewed. ^^ 



For many years chemists speculated on the reason for the 

 predominance of compounds with an even number of carbon 

 atoms among natural fatty acids. The mystery was intensified 

 by such animal feeding experiments as those of Knoop and 

 Dakin," which showed that in mammalian metabolism stepwise 

 degradation of fatty acids and similar substances occurred two 

 carbon atoms at a time. 



Microorganisms have been instrumental in the discovery of 

 the significance of acetate in the cataboUsm and in the biosyn- 

 thesis of fatty acids. The enzymatic methods, particularly those 

 of anaerobic microorganisms, may differ in detail from those of 

 higher animals. This work has been well reviewed. ^^ 



Great advances were made in the discovery of coenzyme A,^*^ 



^- O. Westphal, O. Liideritz, E. Eichenberger and E. Neter, Deut. Z. 

 Verdauungs-u. Stoffivechselkrankh. 15 170 (1955). 



13 E. P. Kennedy, Ann. Rev. Biochem. 26 130 (1957). 



1* H. D. Dakin, "Oxidations and Reductions in the Animal Body," 

 Longmans, Green and Co., London, 1922. 



'^^ H. A. Barker, "Bacterial Fermentations," John Wiley and Sons, 

 Inc., New York, N. Y., 1956, p. 30. 



^® Fritz A. Lipmann, "Les Prix Nobel," Stockholm, 1954. 



