Synthesis of Further Substrates of NAD(P)-Linked Dehydrogenases of High Specific Tritium Content

Abstract

Stereospecific, Hydrogen Labeled The preparation of (R) and (S) [2-³H] lactate as well as (S) [2-³H] glutam ate via the coupled exchange reaction catalyzed by NAD linked dehydrogenases and NADH : lipoam ide oxidoreductase (diaphorase) is described. The specific radioactivity of the hydrogen ions of the ³HOH /H₂O can be obtained in the substrates (100% exchange) if equilibrium isotope effects are disregarded. By the exchange procedure substrates w ith higher specific radioactivity are obtained from positionally [³H] labeled racem ic m ixtures prepared by chemical reductions with [³H] labeled hydrides. The tritium content of one of the enantiom eres is “washed out” into water. As examples are presented the preparation of (R) [2-³H] (S) [2-H] malate as well as the corresponding carnitine, glutam ate and (R) and (S) lactate.