Alanine synthesis from glyceraldehyde and ammonium ion in aqueous solution.

Alanine is formed under anaerobic conditions from glyceraldehyde and ammonium ion in aqueous solutions of sodium phosphate (pH 7.0) or imidazole-imidazolium chloride (pH 7.0) at ambient temperature. In 500 mM imidazole (pH 7.0), alanine synthesis from 10 mM glyceraldehyde and 15 mM ammonium ion is roughly 6 times more rapid in the presence of 10 mM 3-mercaptopropionate (0.62% yield at 60 days) than in its absence (0.10% yield at 60 days). Likewise, the formation of alanine in 500 mM sodium phosphate (pH 7.0) from 5 mM glyceraldehyde and 10 mM ammonium ion is more rapid in the presence of 10 mM N-acetylcysteine than in its absence. In this reaction with N-acetylcysteine, the ratio of the yield of alanine to the yield of lactate is fairly constant. The yield of alanine is about 4.5% that of lactate. Alanine synthesis in the presence of thiol probably proceeds via alanyl thioester, which is produced by rearrangement of the imine of the hemithioacetal of pyruvaldehyde, a product of glyceraldehyde dehydration. The significance of this reaction for molecular evolution is discussed.