Über eine biologische Synthese der Pantothensäure

Abstract

The conc. of pantothenic acid in yeast is below normal when the yeast is grown in medium d ficient in [beta]-alanine. When the conc. of pantothenic acid in the yeast is low, the fermenting capacity, respiration and ability to store glycogen of the yeast are decreased. Some strains of yeast synthesize pantothenic acid from [beta]-alanine and optically active [alpha],[gamma]-dihydroxy-[beta],[beta]-dimethylbutyric acid. In the expts., pantothenic acid is detd. by measuring the turbidity values or growth effect in the Streptobacterium plantarum test. One hundred g. Strain M yeast are shaken for 12 hrs. 3 times with 500 cc. H2O, then 5 times with buffer pH 8, and once with buffer pH 3 and once with buffer pH 10. Since the combined wash fluids contain 37.5% of the pantothenic acid initially present in the yeast, and since the amt. of pantothenic acid in the yeast is not decreased, the yeast must synthesize pantothenic acid from [beta]-alanine and a-hydroxy-[beta][beta]-dimethyl^-butyrolactone contained in the yeast cells. Fifty g. of yeast are frozen \ hr. in liquid N, thawed, frozen again, diluted with an equal vol. of buffer pH 8 and dialyzed while O is bubbled through the soln. 50 hrs. against M/15 phosphate buffer and 20 hrs. against H2O. The yeast now contains no pantothenic acid, but if it is shaken 24 hrs. at 20[degree], pH 5.5, it synthesizes 50% of its original pantothenic acid, and if the two pantothenic acid components are added to the mixture, it synthesizes as much pantothenic acid as was initially present. When this yeast is heated to 80[degree] for 1/2 hr., it loses its capacity to synthesize the acid. The optimum pH for the synthesis is about 8, and the synthesis is decreased by cyanide, octyl alcohol and toluene.