The Enzymatic Synthesis of 5-Hydroxy-N-methylpyroglutamic Acid

Cell-free extracts of Pseudomonas M.A., a nonphotosynthetic bacterium which grows on methylamine as its sole source of carbon, nitrogen, and energy, have been shown to catalyze a reaction between methylamine and a-ketoglutaric acid.The product of this reaction has been identified as the cyclic amide, 5-hydroxy-N-methylpyroglutamic acid.This reaction is catalyzed by an enzyme which diEers from the one catalyzing the formation of N-methylglutamic acid, and it appears to be specific for cr-ketoglutarate.The possibility of a two-step reaction is discussed. 5-Hydroxy-N-methylpyroglutavaate SynthetaseVol. 244, No. 17 TABLEHMPG to free methylamine and a-ketoglutarate(3).This finding suggests that this compound can serve as a substrate for the enzyme in the reverse reaction or that there are other enzymes that can act upon HMPG.Although studies indicate that HMPG is synthesized by whole suspensions of Pseudomonas M.A .,3 the physiological significance of this compound in the metabolism of this organism is still obscure.