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1. Tryptophan synthetase B of three strains of Bacillus subtilis was prepared from ;exo-protoplastic' and ;endo-protoplastic' fractions; the enzyme from ;exo-protoplastic' fraction was purified 30- to 120-fold by ammonium sulphate precipitation and DEAE-cellulose column chromatography; the latter step separated this enzyme from tryptophan synthetase A, tryptophanase and proteolytic enzymes, but the purified preparations were not stable. 2. The activity of tryptophan synthetase B did not depend on the presence of tryptophan synthetase A. 3. Tryptophan synthetases B of the strains tested differed in their utilization of 2- and 7-methylindole as compared with indole; this suggests that these tryptophan synthetases B are not identical.

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Re/erences p. x45/~46. VOL. ~ (i95o) STUDIES OF CITRIC ACID METABOLISM IN HEART MUSCLE ~39 washing (suspension no. 3). Both suspensions contained aconitase and both on addition of boiled muscle extract produced citric acid but did not metabolize it further. On adding bicarbonate to suspension no. 2, an additional amount of citric acid was formed. This did not occur when bicarbonate was added to suspension no. 3. This suggests that suspension no. 2 contains an enzyme system leading to the formation of citric acid which is additional to the system present in suspension no. 3. EXPERIMENTAL MATERIAL AND METHODS Reagents Sodium pyruvats: product of "Hoffmann La Roche", Basle. Citric acid, sodium bi~rbonate, sodium hydroxide: analytical reagents.