Glutaric acid, 2,3-dihydroxy

The appropriateness and essence of this distinction between absolute and relative configuration in this case may be illustrated by a hypothetical experiment. By definition, the determination of an absolute configuration involves a comparison with a fixed reference standard. Such a standard may be simulated by an enzyme that can discriminate between the isomers 16a and 16c, which differ in the configuration of the central atom. If the reacting isomer 16a is represented by (2/ ,3r,4S)-2,4-dihydroxy-3-((/ )-[2-2H]-propionoxy)glutaric acid, it can be predicted with confidence that the enzyme will also react with the enantiomer... 

The substrate directly oxidized to homogentisic acid is p-hydroxy-phenylpyruvic acid. Tyrotine is not at all oxidized in the absence of a-keto-glutarate. 2,5-Dihydroxyphenylalanine, although it is converted to homogentisic acid in the alcaptonuric patient, is not attacked by the soluble enzyme system. Neither is p-hydrox3rphenylacetate nor 2,5-dihydroxy-pyruvate. 

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