VI. FACTOHS REQUIRED IN UMIHATED (JUOWTII MEDIA 589 



it'hiti'd to 1)1- itlciitical willi tin- ".stress factor" in lixcr observed by 

 l"]rshollV"'^ which was capublc of countcractiiiji; the growtli-depressing elfect 

 of thyroid in rats fed a casein diet. 



However, P^rsholf has since shown'"' that lyxofla\in was ineffective as 

 an antithyrotoxic factor when this diet was used. Since the diets employed 

 in the two laboratories differed considerably in composition (soybean-dex- 

 trose versus casein-sucrose), the possibility has been raised (Cooperman 

 c( al.^^^) that lyxoflavin may act as a stimulant in liver factor synthesis by 

 the intestinal flora when the soybean-dextrose diet is employed. Finally, 

 the latter authors were able to demonstrate a slight replacement of ribo- 

 fia\an in rat diets and L. casei growth media, and they concluded that the 

 existing exndence did not warrant the classification of lyxoflavin as a new 

 vitamin. ^Microbiological evidence is inconclusive, for lyxoflavin is stimula- 

 tory both in its own right^"* and as an adjuvant for riboflavin, i"**- ^°^ or is 

 inhibitory.'"^ Thus, the question whether lyxoflavin may be a member of 

 the B complex remains unsettled. Of greater importance, however, is the 

 (juestion whether lyxoflavin can function in metabohsm in any unique fash- 

 ion. Further experiments are in order to definitely establish the natural oc- 

 currence of lyxoflavin, its possible presence in flavoproteins, and its effect 

 upon growth and metabohsm. 



V. Coenzyme III 



Proteus vulgaris was shown by Singer and Kearney""''" to require a 

 previously undescribed cofactor for oxidation of cysteine-sulfinic acid to 

 cysteic acid. Isolation of the factor from bakers' yeast produced a nucleo- 

 tide which was thought by the authors to be identical with nictotinamide- 

 ribose-(o)-pyrophosphate. Because of the similarity to the other nico- 

 tinamide coenzymes, the name coenzyme III was tentatively assigned. 

 Coenzyme III was found in high concentration in yeast and in liver and 

 kidney mitochondria."- In each of these sj^stems, sulfinic dehydrogenase 

 activity was demonstrated, and a fairly general requirement for this co- 

 factor in cysteine metabolism appears possible. 



VI. Factors Required in Unheated Growth Media 



In 1933 Orla- Jensen"* observed that many lactic acid bacteria would not 

 grow properly upon carbohydrates that had been sterilized in distilled 



»»« B. H. Ershoff, Proc. Soc. Exptl. Biol. Med. 73, 459 (1950). 

 '0^ B. H. Ershoff, Proc. Soc. Exptl. Biol. Med. 79, 469 (1952). 

 ">* J. M. Cooperman, W. L. Marusich, J. Scheiner, L. Drekter, E. De Ritter, and S. H. 



Rubin, Proc. Soc. Exptl. Biol. Med. 81, 57 (1952). 

 "9 M. S. Shorb, Proc. Soc. Exptl. Biol. Med. 79, 611 (1952). 

 "0 E. B. Kearney and T. P. Singer, Biochim. et Biophys. Acta 8, 698 (1952). 

 "1 T. P. Singer and E. B. Kearney, Biochim. et Biophys. Acta 8, 700 (1952). 

 >'- T. P. Singer and E. B. Kearney, Federation Proc. 12, 2G9 (1953). 

 "3 A. D. Orla-Jensen, J. Soc. Chem. Ind. 52, 374 (1933). 



