title: Prebiotic formation of 'energy-rich' thioesters from glyceraldehyde and N-acetylcysteine.
abstract: The 'energy-rich' thioester, N-acetyl-S-lactoylcysteine, is formed from low concentrations of glyceraldehyde and N-acetylcysteine under anaerobic conditions at ambient temperature in aqueous solutions of sodium phosphate (pH 7.0).  Reactions with 2 mM glyceraldehyde, 2 mM N-acetylcysteine, and 500 mM sodium phosphate (pH 7.0) convert about 3%/day of the glyceraldehyde to lactoyl thioester.  The formation of lactoyl thioester in similar reactions with 500 mM imidazole hydrochloride (pH 7.0) is supported by the thiol-dependence of lactate formation, which is 3-fold greater in the presence of thiol (0.11%/day) than in the absence of thiol (0.04%/day).  The formation of lactoyl thioester is thought to proceed by the phosphate (or imidazole)-catalyzed dehydration of glyceraldehyde to give pyruvaldehyde, which adds to the thiol to form a hemithioacetal that rearranges to the thioester.  A limited amount of a second thioester, N-acetyl-S-glyceroyl-cycsteine, is also formed at the beginning of these reactions.  The significance of these reactions to the origin of life is discussed.
authors.affiliation: The Salk Institute for Biological Studies, San Diego, CA 92138, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Weber
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D001704:Biopolymers; D019418:Evolution, Chemical; D005985:Glyceraldehyde / Q000031:analogs & derivatives / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D019344:Lactic Acid / Q000138:chemical synthesis; D000069497:Origin of Life; D010710:Phosphates / Q000737:chemistry; D010766:Phosphorylation; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis
chemical_list: D001704:Biopolymers; D007093:Imidazoles; D010710:Phosphates; D013438:Sulfhydryl Compounds; D019344:Lactic Acid; D005985:Glyceraldehyde; C035741:N-acetyl-S-lactoylcysteine; C042609:N-acetyl-S-glyceroylcysteine; C018279:sodium phosphate; D000111:Acetylcysteine