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The physical properties and the effects of detergent on the activities of purified NAD-linked a-glycerophosphate dehydrogenase(EC 1.1.1.8, GPDH) from kidney, liver and skeletal muscle of the rat were studied. The activity of this enzyme was measured by the method of White and Kaplan. The enzyme activity of liver (9.65 units/g tissue) was higher than those of other organs, but the highest value of the specific activity was shown in skeletal muscle as 0.058 unit/㎎ protein. These enzymes were purified approximately 167, 286 and 216-fold from kidney, liver and skeletal muscle, respectively, by ammonium sulfate saturation and blue dextran Sepharose column chromatography. These enzymes were composed of two isozymes which have different isoelectric points. Isoelectric points of the two isozymes were 6.5 and 6.7, and the molecular weights were 62,000 and 60,000 daltons. The UV spectrums of the purified enzymes from three organs of the rat showed very simillar pattern. But the representative compounds from three classes of detergents showed different effects on these enzymes. The enzyme of the skeletal muscle was activated by all of the detergents which were studied expect for Triton X-100, whereas the enzymes of the kidney and the liver were not activated or strongly inhibited by all of the detergents. In conclusion, the purified a-glycerophosphate dehydrogenases from the three organs of the rat were the homogeneous proteins out of consideration for physical properties. But the differences in the interaction between enzymes and detergents revealed that there are unsimilarities in the three dimentional structure between the skeletal muscle and those of other two organs inspite of similarities between the enzyme of kidney and that of liver.
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