Intracellular localization of thiamin accumulated in baker's yeast

Yeast accumulates large quantities of thiamin from thiamin-containing solutions. The intracellular localization of thiamin and thiamin pyrophosphate accumulated in baker's yeast was studied. About 40% of both thiamin and thiamin pyrophosphate were released during protoplast preparation. After homogenization of the protoplasts and fractionation of the homogenate, most of the thiamin and thiamin pyrophosphate remaining in the protoplasts were found in the S2 fraction (20, 000×g supernatant fraction), although some was also recovered in the P2 fraction (20, 000×g pellet fraction). The activity of a mitochondria-marker enzyme, succinate dehydrogenase was mostly found in the P2 fraction and that of α-glucosidase, a cytosol-marker was found exclusively in the S2 fraction, indicating that P2 was particulate and that S2 was mostly non-particulate.