Spectroscopic Probes of Hydride Transfer Activation by Enzymes

Spectroscopic Probes of Hydride Transfer Activation by Enzymes... 

Substitution of the active site Zn(II) of LADH by Co(II), Ni(II), Cu(II), or Fe(II) introduces spectroscopic probes, which are sensitive to the coordination geometry, the electrostatic environment, and the protein conformation. UV-visible absorbance signatures consisting of d- d and ligand-to-metal charge transfer (LMCT) transitions have proven to be useful probes of the site environment (3, 24-26, 29, 34, 35). The Co(II) and Ni(II) derivatives exhibit catalytic parameters (i.e., hydride transfer rates, Km and lq values) that are similar to those of the native Zn(II)-enzyme (25). The Cu(II) and Fe(II) enzymes show reduced reactivities and catalytic parameters, which indicate these derivatives are of limited use as analogues of the native enzyme (24). 

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