[Storage of 14C-thiamine in rat liver subcellular fractions]

Distribution of 14C thiamine and its incorporation into TPP-dependent enzymes of rat liver subcellular fractions were studied. Thiamine was stored mainly in hyaloplasm and mitochondria. In nuclear and microsomal fractions presence of the vitamin was due to contamination by hyaloplasm components during the destruction of liver cells. In the proteins of hyaloplasm the label was incorporated in transketolase only. On the basis of these findings a procedure for isolation of the enzyme was developed. The purification process of monitored by calculation of specific radioactivity instead of the specific enzymatic activity of transketolase. In the mitochondria 14C-TPP was incorporated only into alpha-keto acid dehydrogenase complexes; transketolase was not found in the mitochondria. Metabolism of subcutaneously injected 14C-thiamine was studied in liver mitochondria and hyaloplasm.