Enzyme-substrate complex without metals

The NADP-IDH from Escherichia coli has been thoroughly studied. It is a dimeric protein of two identical 40-kDa subunits. High-resolution X-ray crystal structures have been determined for the enzyme with and without substrate [16,17], and for the pseudo-Michaelis complex of the enzyme with isocitrate and NADP [18], Structures of sequential intermediates formed during the catalytic action of IDH are also available [19], Additionally, the kinetic and catalytic mechanisms have been determined in detail [20], Amino acid residues which are involved in interactions with substrate, coenzyme, metal ions, and catalysis have been identified [10,21],... 

Co(lII), or Rh(lII), which form inert complexes with nucleotides that exchange ligands on the time scale of days or weeks (especially at low temperatures). It is possible, for example, to separate the A and A isomers of CrATP and use them as substrates in single turnover experiments with various enzymes 23, 24). When the enzyme catalyzes multiple turnovers, the developing circular dichroic (CD) spectrum as one isomer is converted to a product without a CD spectrum can determine the screw-sense specificity. Thus, hexokinase and glycerokinase use the A isomer of CrATP as a substrate, and pyruvate kinase and myokinase (adenylate kinase) use the A isomer (25). The absolute configurations of the ADP and ATP complexes of these metal ions are now known and have been correlated with the CD spectra (26-30). 

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