438 THIAMINE 



N— CH CI CH3 



II I II 



CH3— C— C -CH2 N— C O O 



II \ II II 



N=C O C— CH2— CH2O— P— O— P— OH 



I II / II 



HN— P— OH H— C— S OH OH 



I 

 OH 



In the polyphosphates still more phosphate groups are attached to the 

 pyrimidine nucleus. The name cocarboxylase hs been reserved for the thia- 

 mine pyrophosphate. 



Cocarboxylase can be synthesized from thiamine chemically or enzj^mi- 

 cally. However, because carboxylase is not dissociated (see below), the en- 

 zymic synthesis stops when the apoenzyme is saturated. No preparative use 

 can therefore be made of this reaction. 



1. Chemical Procedure 



Lohmann and Schuster^'' described a method for preparing the cocarboxy- 

 lase. Weyland and Tauber^^ gave an extensive description for the prepara- 

 tion of thiamine pyrophosphate which substance Weil-Malherbe^^ synthe- 

 sized by treating the thiamine bromide with silver pyrophosphate. Karrer 

 and Viscontini^^ improved the method of Weyland and Tauber. The strong 

 hydrochloric acid that is present during the procedure of Weyland and 

 Tauber^^ tended to hydrolyze a large part of the thiamine pyrophosphate 

 to monophosphothiamine. Therefore Karrer and Viscontini^^ improved the 

 method by preparing the phosphate of the cocarboxylase. In this way they 

 reduced the acidity of the solution and so obtained a yield that was 55 % 

 of the calculated one. 



2. Enzymic Synthesis 



Yeast, bacteria, and animal tissues contain systems that are able to 

 phosphorylate thiamine. The first reports (von Euler and Vestin"; and 

 Lohmann and Schuster^^) needed confirmation because thiamine strongly 

 stimulates cocarboxylase activity (see Section IV A, p. 425). Ochoa and Pe- 

 ters^* and Ochoa et al.^^ studied the phosphorylation process in animal 

 tissues. They found that liver shows a particularly good phosphorylating 

 capacity. Slices, brei, and "dispersions" were equally active. Brain and 

 muscle were much less active; preparations from duodenal mucosa (pig) 



^4 J.. Weyland and H. Tauber, ./. .1//;,. Chem. Sac. 60, 2263 (1938). 

 "5 H. Weil-Malherbe, Biochem. J. 34, 980 (1940). 

 '6 P. Karrer and M. Viscontini, Helv. Chirn. Acta 29, 1901 (1946). 

 '' H. von I'mler and R. Vcstin, Naturwissenschnftcn 25, 416 (1937). 



