TABLE 2.

β-Lyase specific activities (nmol mg protein^-1 min^-1) toward THT-A in selected rat tissues^a

	Homogenate	Cytosol	Mitochondria
Liver
No addition	0.69±0.02	1.06±0.29	4.01±0.13
+ 5 mM D,L-Propargylglycine	0.19±0.04*	0.23±0.11*	2.79±0.17**
+ 0.5 mM KG	0.75±0.06	1.34±0.14	3.66±0.52
+ 0.5 mM KMB	0.65±0.06	1.23±0.32	2.50±0.33***
Kidney
No addition	1.18±0.09	ND	ND
Brain
No addition	0.23±0.03	ND	ND

^aThe 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 in the Materials and Methods section. 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 prior to addition of the 2,4-dinitrophenylhydrazine reagent. A correction was made for the slow non-enzymatic conversion rate of THT-A to pyruvate under the incubation conditions (n = 3 to 6 determinations). ND, not determined. The amount of protein (μg) in each assay mixture was as follows: liver homogenate (324), liver cytosol (53), liver mitochondria (43), kidney homogenate (76) and brain homogenate (160). The time of incubation (min) was as follows: liver homogenate (30), liver cytosol (120), liver mitochondria (120), kidney homogenate (120) and brain homogenate (120).

Significant differences between “no addition” and “addition” values are

^*P = 0.05

^**P = 0.025

^***P = 0.0025.