632 PANTOTHENIC ACID 



combined in a disulfide linkage with any of several naturally occurring 

 — SH compounds.^"' ^^ Linkage 1 is cleaved by intestinal phosphatase. ^^ 

 Hydrolysis of linkage 2, accomplished by an enzyme preparation from 

 pigeon or chicken liver/^ liberates a fragment, B. Hydrolysis of linkage 3, 

 accomplished by a potato pyrophosphatase,^^ should liberate 4-pho8pho- 

 pantetheine. Hydrolysis of both linkages 2 and 3, by the combined action 

 of pyrophosphatase and the liver enzyme, would yield a pantothenic acid 

 phosphate. Synthetic phosphates of pantothenic acid, in contrast to panto- 

 thenic acid, are stable to alkali ;2*' ^* an alkali-stable form of the vitamin 

 that occurs naturally and is converted to an alkali-labile form by treat- 

 ment with phosphatases*^ may be identical with this fragment. Liberation 

 of free pantothenic acid, C, from coenzyme A requires the combined action 

 of the liver enzyme and intestinal phosphatase*^ • *^ to hydrolyze linkages 1 

 and 2. 



Of these compounds, only LBF (A) and free pantothenic acid (C) have 

 growth-promoting activity for lactic acid bacteria, and only free panto- 

 thenic acid has such activity for yeasts.^^ The activity of LBF is much 

 greater than that of pantothenic acid for one group of lactic acid bacteria 

 but is equal to or less than that of pantothenic acid for Lactobacillus casei 

 and Lactobacillus arabinosus, the organisms commonly used for assay of 

 pantothenic acid. Whichever of the methods of assay is used, it is therefore 

 necessary to liberate pantothenic acid by the combined action of liver 

 enzyme and intestinal phosphatase to obtain true values. Procedures for 

 this purpose have been summarized elsewhere.*^- *^-*^ Since such procedures 

 were unknown until recently, many of the early figures for the pantothenic 

 acid content of natural materials obtained by microbiological procedures are 

 low, a fact that was indicated quite early by their failure to agree with 

 chick assay procedures.*' 



The most widely used microbiological procedure for pantothenic acid 

 employs Lactobacillus arabinosus as the test organism.*^ The procedure and 

 medium are very similar to those used for determination of biotin and nico- 

 tinic acid; they have been described in detail several times.*^"*' Growth 

 in the pantothenic acid-free medium increases with the pantothenic acid 



s" G. M. Brown and E. E. Snell, Proc. Soc. Exptl. Biol. Med. 77, 138 (1951). 



31 G. M. Brown and E. E. Snell, J. Biol. Chem. 198, 375 (1952). 



32 G. D. Novelli, N. O. Kaplan, and F. Lipmann, J. Biol. Chem. 177, 97 (1949). 



33 G. D. Novelli, N. O. Kaplan, and F. Lipmann, Federation Proc. 9, 209 (1950). 

 3* T. E. King and F. M. Strong, Science 112, 562 (1950). 



36 A. L. Neal and F. M. Strong, /. A?n. Chem. Soc. 65, 1659 (1943). 



36 J. B. Neilands and F. M. Strong, Arch. Biochem. 19, 287 (1948). 



37 E. E. Snell, in Vitamin Methods, Vol. I, p. 327. Academic Press, 1950. 



38 Association of Vitamin Chemists, Methods of Vitamin Assay, 2nd ed., p. 290. In- 

 terscience Publishers, New York, 1951. 



39 T. H. Jukes, Biol. Symposia 12, 253 (1947). 



