title: Metal binding to D-lactate dehydrogenase.
abstract: The kinetic and spectral properties of native and cobalt-substituted D-lactate dehydrogenase have been compared. Optical and MCD spectra are consistent with high-spin tetrahedral cobalt. The cobalt enzyme is strongly inhibited by D-lactate when oxygen is the electron acceptor. This is probably due to the formation of an abortive complex of reduced enzyme and lactate. Like the native zinc enzyme, the cobalt-substituted enzyme is reduced by substrate in a triphasic fashion involving a transient charge-transfer complex. The kinetics of the cobalt enzyme suggest that the metal is involved in substrate binding and reduction. A second metal-binding site is also described. Evidence is presented to suggest that the flavin cofactor and an essential thiol are involved in this site.
mesh_terms: D001665:Binding Sites; D003035:Cobalt / Q000378:metabolism*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000378:metabolism*
chemical_list: D008670:Metals; D003035:Cobalt; D007770:L-Lactate Dehydrogenase; D015032:Zinc