Alanine-dependent reactions of 5'-deoxypyridoxal in water.
The non-enzymatic reaction of 5'-deoxypyridoxal (DPL) with l-alanine in water at 25 degrees C was investigated. DPL reacts with alanine to form an imine, which then undergoes deprotonation at the alpha-amino carbon of alanine to form a resonance delocalized DPL-stabilized carbanion. At early reaction times the only detectable products are pyruvate and the dimeric species formed by addition of the alpha-pyridine stabilized carbanion to DPL. No Claisen-type products of addition of the alpha-amino carbanion to DPL, as was previously reported to form from the reaction between DPL and glycine [K. Toth, T.L. Amyes, J.P. Richard, J.P.G. Malthouse, M.E. Ni Beilliu, J. Am. Chem. Soc. 126 (2004) 10538-10539], are observed. The electrophile reacts instead at the alpha-pyridyl carbon. This dimer is in chemical equilibrium with reactants. At longer reaction times about 50% of DPL is converted to 5'-deoxypyridoxamine, the thermodynamically favored product of formal transamination of DPL.
Go
Maybelle K
MK
Department of Chemistry, University at Buffalo, SUNY, Buffalo, NY 14260, USA.
Richard
John P
JP
D000409:Alanine / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D019281:Dimerization; D005998:Glycine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D011730:Pyridoxal / Q000031:analogs & derivatives* / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D014867:Water; C001609:5-deoxypyridoxal; D011730:Pyridoxal; D002244:Carbon; D000409:Alanine; D005998:Glycine