title: Inhibition of lactate production in rat brain extracts and synaptosomes by 3-[4-(reduced 3-pyridine aldehyde-adenine dinucleotide)]-pyruvate.
abstract: In basic solutions, pyruvate enolizes and reacts (through its 3-carbon) with the 4-carbon of the nicotinamide ring of NAD+, yielding an NAD-pyruvate adduct in which the nicotinamide ring is in the reduced form. This adduct is a strong inhibitor of lactate dehydrogenase, presumably because it binds simultaneously to the NADH and pyruvate sites. The potency of the inhibition, however, is muted by the adduct's tendency to cyclize to a lactam. We prepared solutions of the pyruvate adduct of NAD+ and of NAD+ analogues in which the -C(O)NH2 of NAD+ was replaced with -C(S)NH2, -C(O)CH3, and -C(O)H. Of the four, only the last analogue, 3-[4-(reduced 3-pyridine aldehyde-adenine dinucleotide)]-pyruvate (RAP) cannot cyclize and it was found to be the most potent inhibitor of beef heart and rat brain lactate dehydrogenases. The inhibitor binds very tightly to the NADH site (Ki approximately 1 nM for the A form). Even at high concentrations (20 microM), RAP had little or no effect on rat brain glyceraldehyde-3-phosphate, pyruvate, alpha-ketoglutarate, isocitrate, soluble and mitochondrial malate, and glutamate dehydrogenases. The glycolytic enzymes, hexokinase and phosphofructokinase, were similarly unaffected. RAP strongly inhibited lactate production from glucose in rat brain extracts but was less effective in inhibiting lactate production from glucose in synaptosomes.
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D007773:Lactates / Q000096:biosynthesis*; D019344:Lactic Acid; D009243:NAD / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects
chemical_list: D007773:Lactates; D009243:NAD; C052497:3-(4-(reduced 3-pyridine aldehyde-adenine dinucleotide))pyruvate; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase