TABLE 2

β-Lyase specific activities (nmol/mg protein/min) toward THT-A in selected rat tissues The standard reaction mixture (20 μl) contained 5 mM THT-A, 100 mM potassium phosphate buffer, pH 7.4, and the indicated tissue fraction. After incubation at 37°C, pyruvate was determined by the 2,4-dinitrophenylhydrazone procedure as outlined under Materials and Methods. The blank contained phosphate buffer plus tissue fraction incubated at 37°C. At the end of the incubation period, 2 μl of 50 mM THT-A was added just before addition of the 2,4-dinitrophenylhydrazine reagent. A correction was made for the slow nonenzymatic conversion rate of THT-A to pyruvate under the incubation conditions (n = 3–6 determinations). The amount of protein in each assay mixture was as follows: liver homogenate (324 μg), liver cytosol (53 μg), liver mitochondria (43 μg), kidney homogenate (76 μg), and brain homogenate (160 μg). The time of incubation was as follows: liver homogenate (30 min), liver cytosol (120 min), liver mitochondria (120 min), kidney homogenate (120 min), and brain homogenate (120 min). Significant differences between “no addition” and “addition” values are ^*p = 0.05, ^**p = 0.025, and ^***p = 0.0025.