Co-Carboxylase (Vitamin B 1 -Pyrophosphate) Content of Plants

Abstract

Lohmann and Schuster 1 , 2 have shown that co-carboxylase is identical with the pyrophosphoric ester of vitamin B₁. I have demonstrated recently 3 , 4 that synthetic vitamin B₁ is readily phosphory-lated by the duodenal mucosa and by extensively washed dry yeast which had been freed of co-carboxylase. The enzymic synthesis of vitamin B₁ -pyrophosphate occurs best at a slightly acid pH. Euler and Vestin, 5 and Kinnersley and Peters 6 independently and at the same time when I published my experiments have also shown that yeast converts vitamin B₁ to co-carboxylase.

The enzyme carboxylase has an important part in carbohydrate metabolism. It is widely distributed in nature and it is accompanied by its coenzyme. It occurred to me that a quantitative study of a series of plants for co-carboxylase and comparing these findings with the vitamin B₁ content of the plant material may be of interest.

The well ground plant tissues were extracted by boiling for 5 minutes with 3 to 5 times their weight of pH 6.239 phosphate (Sorensen). In 2 cc. of the clear nitrates co-carboxylase was determined according to Lohmann and Schuster. 1 In Column 1 of Table I, figures obtained for co-carboxylase are shown and in Column 2, figures for vitamin B₁ content of these plant materials as obtained by biological assay are given. By comparing these figures with that which I have obtained for the enzymatically synthesized co-carboxylase (not completely phosphorylated) it may be seen that only a small part of the total vitamin B₁ is present in these plants in the form of its pyrophosphoric ester. It should be noted, however, that there is no direct proportionality between CO₂ formation and the amount of co-carboxylase added, especially when too large amounts of the co-enzyme are to be estimated. For this reason in the case of dry yeast only 0.3 cc. of boiled yeast juice equivalent to 50 mg. of dry yeast was employed for the test. The results show that phosphorylation of vitamin B₁ by the mammalian organism is of vital importance as this co-enzyme plays an important rôle in the decarboxylation and dehydrogenation of pyruvic acid. 8 Furthermore animal tissues contain all of the vitamin B₁ as the pyrophosphoric ester. 8