Apoenzyme stimulation test

The following study illustrates the use of the apoenzyme stimulation test. Human subjects were involved, The study was used to help determine the daily require-... 

Apoenzyme stimulation test, 547-548 Apo E recL ptor, 333 Apo-heme, 753, 755,75f)... 

FIGURE 9.39 Results of an apoenzyme stimulation test. (Reprinted with permission from Linkswiler, 1967.)... 

The glutamate-oxaloacetate aminotransferase stimulation test involves the reconstitution of PLP with the apoenzyme. The enzyme activity in broken red blood cells is measured with and without PLP added. Addition of PLP would be expected to result in little or no stimulation of enzyme activity if the subject had been consuming a Bg-adequate diet, whereas an increase in enzyme activity with the addition of pure PLP to the enzyme assay mixtures would indicate that the subject had been consuming a Bg-deficient diet. Consumption of a Bg-deficient diet allows continued synthesis of the apoenzyme in the cell, but not conversion of the apoenzyme to the holoenzyme. A marked increase occurring with the addition of PLP could indicate that the subject had been consuming a Bg-deficient diet or that absorption of dietary vitamin Bg was impaired or defective in some way. 

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