442 THIAMINE 



is necessary, preferably with pure pyruvodehydrogenase preparations, to 

 establish the mechanism for the oxidative activity of thiamine pyrophos- 

 phate. 



V. specificity of Action 



B. C. P. JANSEN 



A. THE ESSENTIAL METALS 



Most of the carboxylases are thiamine pyrophosphate-magnesium-pro- 

 tein compounds (Ochoa^). Magnesium may be replaced by manganese. 

 Green et al? using a preparation from top brewer's yeast, made an elaborate 

 study of the replacement of magnesium by other metals. All the divalent 



metals tested could replace magnesium. The trivalent form of iron and the 

 trivalent aluminum were practically inactive (Table II). 



Stumpf^ in his pyruvic oxidase from Proteus vulgaris replaced the Mg by 

 Mn=, Fe=, Ni=, Zrr or Co=, but Ca=, Ba=, Cd= and the trivalent Fe- and 

 Al- were ineffective. Green et at} stated that their preparation of diac- 

 etyl mutase from pigeon breast muscle did not require magnesium or any 

 other divalent metal. 



B. THIAMINE PYROPHOSPHATE 



In pure preparations not containing a phosphorjdating system, thiamine 

 pyrophosphate cannot be replaced by thiamine, monophosphothiamine, 

 pyrithiamine (Stumpf^), diphosphopyridine nucleotide, triphosphoropyri- 

 dine nucleotide, flavin dinucleotide, adenosinetriphosphate, or pyridoxal 

 phosphate (Green et al}). 



1 S.Ochoa, Biochem. J. 33, 1262 (1939). 



2 D. E. Green, D. Herbert, and V. Subrahmanyan, J. Biol. Chcm. 138, 327 (1941). 



3 P. K. Stumpf, /. Biol. Chem. 159, 529 (1945). 



^D. E. Green, P. K. Stumpf, and K. Zarudnaya, J. Biol. Chem. 167, 811 (1947). 



