Re-face stereospecificity of NADP dependent methylenetetrahydromethanopterin dehydrogenase from Methylobacterium extorquens AM1 as determined by NMR spectroscopy

MtdA catalyzes the dehydrogenation of N-5,N-10-methylenetetrahydromethanopterin (methylene-H4MPT) with NADP(+) as electron acceptor, In the reaction two prochiral centers are involved, C14a of methylene-H4MPT and C4 of NADP(+), between which a hydride is transferred. The two diastereotopic protons at C14a of methylene-H4MPT and at C4 of NADPH can be seen separately in H-1-NMR spectra, This fact was used to determine the stereospecificity of the enzyme. With (14aR)-[14a-H-2(1)]-[14a-C-13]methylene-H4MPT as the substrate, it was found that the pro-R hydrogen of methylene-H4MPT is transferred by MtdA into the pro-R position of NADPH. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B,V, All rights reserved.