The authors (1) have reported a study on the contribution of vitamin B12 (B12) to the formation of carboxylase in B12-deficient rats. The increase in car boxylase activity was always observed in the group receiving vitamin B12, whereas it was negative in the B12-deficient group. These experiments were repeated and the addition of vitamin B12 to the diet was confirmed to increase the formation of carboxylase (2).
It is well known that the enzymatic formation of diphosphothiamine (DPT) takes place with adenosine triphosphate (ATP) as a phosphorylating agent. K. Lohmann and P. Schuster (1) first found that the extracts of the brain and other tissues could serve as the sources of the specific transphosphorylating enzymes. F. Leuthardt and H. Nielsen (2) repeated the experiments and demonstrated the conversion of thia mine to DPT in many animal tissues and microorganisms with participation of ATP. K. H. Kiessling (3) observed yeast cells to convert thiamine to mono-and tripho sphothiamine, neither of which alone had cocarboxylase activity However, Rossi Fanelli (4) showed the pure triphosphothiamine isolated from yeast to be able to activate rat-liver pyruvate oxidase system similarly to DPT. N. Shimazono (5) de monstrated more enzymatic formation of DPT by yeast enzyme at certain pH levels when inosine or guanosine-triphosphate was added in place of ATP. He also found the latter triphosphates to be replaceable by inosine-monophosphate (IMP) plus ATP or guanosine-monophos phate plus ATP. No further investigation on the acti
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