The localization of aneurin pyrophosphatase in the brain.

Vitamin B1 is nearly exclusively present in animal tissues as aneurin pyrophosphate (Ochoa and Peters, 1938). The vitamin is first converted to aneurin pyrophosphate by the tissues and in this form it enables the oxidative decarboxylation of pyruvic acid to take place allowing glucose metabolism to go beyond the pyruvate stage (Banga, Ochoa, and Peters, 1939). It has been shown more recently that aneurin pyrophosphate participates in other metabolic processes in nervous tissue (Green, Stumpf, and Zarudnaya, 1947). With regard to pyruvate oxidation, Banga and his colleagues (1939) found that free aneurin is more effective than aneurin pyrophosphate in stimulating the respiration of brain preparations from vitamin B1-deficient animals. A possible explanation of this finding is that the tissue is poorly permeable to aneurin pyrophosphate but more permeable to aneurin. Aneurin consequently is able to pass the permeability barriers, become phosphorylated and be available to act as the co-enzyme. This view presupposes some dephosphorylating mechanism' in the living animal whereby aneurin pyrophosphate is degraded to free aneurin. The dephosphorylation of aneurin pyrophosphate by brain tissue was observed by Ochoa (1939). Westenbrink, Parve, and Goudsmit (1943) described an active phosphatase hydrolysing the phosphoric esters of aneurin. It was found that this enzyme successively removes the two phosphate groups from aneurin pyrophosphate, so that when the terminal phosphate is removed, aneurin orthophosphate appears as the intermediary which is further broken down, releasing aneurin. The histological demonstration in brain tissue of the sites of this hydrolytic process is of interest in relation to the pathology of those nervous diseases associated with aneurin deficiency. This paper describes and illustrates the results obtained from localizing in brain tissue the sites of enzymatic cleavage of phosphate from aneurin pyrophosphate at pH 6-9. Method