Abstract
Summary
The kinetic effect of the four stereoisomers of ascorbic acid upon the activity of p-hydroxyphenylpyruvate oxidase was studied. Average Michaelis constants for the four stereoisomers, obtained at a p-hydroxyphenylpyruvate concentration of 1.6 × 10-5 M, were: D-xyloascorbate, 2.5 × 10-5 M; L-araboascorbate 3.8 × 10-5 M; and L-xyloascorbate, 4.0 × 10-5 M; and D-araboascorbate, 6.7 × 10-5 M. V′max values were very similar. The small changes in K′ acs demonstrate an ascorbate stereospecificity in the pHPP oxidase reaction, but it does not appear large enough to explain known nutritional effects.
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