VITAMINS 191 



pounds (or both) before it combines with the protein portion (apoenzyme) 

 of the enzyme system. The pyrophosphoric ester of thiamine is known 

 as cocarboxylase, or as thiamine pyrophosphate. This compound is the 

 coenzyme of carboxylase. 



CH, O O 



N=C— NH2 I II II 



I C=C— CH2— CH2— O— P~0— P— OH 



CH3— C C— CH2— N 



o 



H H 



i 



CI CH— S 



N— CH 



Thiamine pyrophosphate (cocarboxylase) 



This substance is as active as thiamine (mole for mole) . Lilly and Leonian 

 (1940) compared the action of thiamine and thiamine pyrophosphate on 

 several thiamine-deficient fungi. No significant differences were found 

 in the maximum weights of mycelium formed in the presence of equivalent 

 quantities of these two growth factors. The rate of early growth was 

 greater with thiamine pyrophosphate than with thiamine for Phyco- 

 myces hlakesleeanus and less for Mucor ramannianus and Phytophthora 

 erythroseptica. 



Pyruvic acid, one of the key intermediate products of carbohydrate 

 metabolism, is transformed into carbon dioxide and acetaldehyde by the 

 action of the enzyme carboxylase. Pyruvic acid accumulates in the 

 culture media of many thiamine-deficient fungi when insufficient thiamine 

 is present. Haag and Dalphin (1940) found that the maximum accumu- 

 lation in Phycomyces hlakesleeanus cultures occurred when about one- 

 twentieth of the optimum amount of thiamine was added. Wirth and 

 Nord (1942) studied the effect of added thiamine upon the accumulation 

 of pyruvic acid in cultures of Fusarium lini, a self-sufficient fungus with 

 respect to thiamine. Some of the data are presented in Table 34. 



The accumulation of pyruvic acid in the culture medium is common, 

 especially during the early period of growth. Pyruvic acid may be 

 detected qualitatively by adding of iodine solution (KI3) to the culture 

 filtrate and making the solution strongly alkaline with sodium hydroxide. 

 Iodoform is produced instantly without heating. Acetaldehyde, which is 

 very volatile, also reacts with iodine and alkali in the cold to produce 

 iodoform. Sordaria fimicola, Lenzites trahea, or other fungi which produce 

 acid during the early stages of growth may be used to demonstrate the 

 production of pyruvic acid. 



Specificity. So far as is known, thiamine which occurs in nature has 

 the structure given in the formula. This vitamin has been isolated from 

 only a few substances such as wheat germ and rice polish. The ethyl 

 homologue (ethyl in place of methyl in position 2) of thiamine is slightly 

 more active for certain fungi than ordinary thiamine. Higher homologues 



