II. CHEMISTRY 93 



o. K.vislencc of- an Acid-Labile Chick And- Anemic Factor in Liver 



In the isolation of \itamin Be (P(iA) from horse hver, Pfiffner ct o/.'" 

 described certain fractions whose activity for chicks and L. casei was in- 

 activatedhy acid conditions wliichhad no effect on puie P(1A. Concentrates 

 c()nt:iiiiin,<>; this a('i(l-hil)ile factor contained twice as much POA activity 

 by S. faeralis as by /.. casci assay. After acid treatment in l.o% inethanol- 

 hy(h-ofi;en chloiide, the L. casci activity decreased to 20 to 30% of its 

 original valne and the activity as measured by the two organisms became 

 the same. A similar treatment of pure PGA produces insignifi(;ant losses in 

 activity. The zinc salt of the acid-labile factor is more soluble than that of 

 PCi.V. There has been some speculation that this acid-labile foim may be 

 the citrovorum factor or a related compound. The acid lability properties 

 of the citrovorum factor correspond roughly with those of the acid-labile 

 form. However, the acid lability of citrovorum factor is less than that of 

 the acid-labile form of PGA obtained by Pfiffner. Until further evidence is 

 available, no definite conclusions can be drawn regarding the identity of 

 these two compounds. 



2. Of PGA Conjugates 



Soon after it ])ecame apparent that the growth factor for L. casci was also 

 involved in animal nutrition, evidence was obtained by Welch and Wright'^ 

 which .showed that milk possessed more activity for animals than could be 

 accounted for on the basis of its microbiological activity. Similarly IMallory 

 et a/.*"* noted that yeast concentrates were more active in promoting growth 

 and preventing leucopenia in rats fed sulfasuxidine (succinylsulfathiazole) 

 than liver preparations containing up to fifteen times as much ''Strepto- 

 coccus lactis R-stimulating factor." These workers also pointed out the 

 parallelism between the activity of liver and yeast preparations for the 

 sulfonamide-fed rat and for the vitamin M-deficient monkey, and the lack 

 of parallelism with the microbiological activity. They also suggested that 

 the.se yeast preparations contained potential "Streptococcus lactis R-stimu- 

 lating factors" which could be enzymaticalh' converted to microbiologically 

 active compounds. 



A conjugated form of PGA which is much more active for /.. casci than 

 for S.faccolis was described by Ilutchings ef a/.'^ This compound, which was 



'3 A. D. Welch and L. D. Wright, Science 100, 153 (1944). 



"M. E. Mallory, V. Mims, J. R. Totter, and P. L. Day, ./. Biol. Chcm. 156, 317 



(1044). 

 '* li. L. Hutfhings, E. L. R. Stokstad, X. Bohono.s, and X. H. Slohodkin, Science 



99, 371 (1944). 



