Proton magnetic resonance studies of alpha-keto acids.
J Biol Chem, 1975/1/25;250(2):527-32.
PMID: 234430
Abstract
Pulsed Fourier transform proton magnetic resonance was used to study alpha-ketoglutaramic, and several other alpha-keto acids in aqueous solutions as a function of pH. Most alpha-keto acids were found to exist in equilibrium with the hydrate (gem-doil). The equilibrium position favors the nonhydrated alphs-keto acid at neutral pH, but at low pH values (below the pKa of the alpha-carboxylic acid group) the hydrate predominates. We found evidence that alpha-ketoglutaric acid exists in a third equilibrium form which is assigned to the lactol. alpha-Ketoglutaramic acid (the alpha-keto acid analog of glutamine) which is known to exist predominantly in a cyclic form at pH 7.0 was shown to exist as a cyclic structure over a wide pH range. However, the cyclic form is an equilibrium mixture of 2-pyrrolidone-5-hydroxy-5-carboxylic and 1-pyrrolin-2-one-5-carboxylic acids.
MeSH terms
Deuterium; Glyoxylates; Hydrogen-Ion Concentration; Keto Acids; Ketoglutaric Acids; Kinetics; Magnetic Resonance Spectroscopy; Molecular Conformation; Pyruvates; Structure-Activity Relationship; Water
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