Dehydrogenase enzyme/coenzyme/substrate interactions

Resonance Raman spectra of several apo and holodehydrogenase enzymes excited with ultraviolet laser wavelengths are reported. At 260 nm maximum selective enhancement of the NAD and NADH coenzyme vibrational spectra is seen and effects associated with the coenzyme binding to the several different enzymes are attributed to polarity and hydrogen bonding between adenine component and amino acid residues at the enzyme binding sites. With 220 nm excitation the aromatic amino acid residues dominate the RR vibrational spectra while 240 nm excitation is selected to probe the acyl enzyme intermediate in the reaction of glyceraldehyde3phosphate dehydrogenase (GAPDH) with its substrate GAP. Comparisons are made with recent results from normal nonresonance Raman studies and finally new data on inelastic neutron scattering (INS) are presented. 2.