The role of the metal ion in the mechanism of the K+-activated aldehyde dehydrogenase of Saccharomyces cerevisiae.
The effect of K+ on assays of the enzyme was studied and it appears that the activation occurs slowly by a two-step process. Kinetic measurements suggest that the enzyme-catalysed reaction can proceed slowly (0.4%) in the complete absence of K+. The enzyme exhibits a K+-activated esterase activity, which is further activated by NAD+ or NADH. Stopped-flow studies indicated that the principal effect of K+ on the dehydrogenase reaction is to accelerate a step (possibly acyl-enzyme hydrolysis) associated with a fluorescence and small absorbance transient that occurs after hydride transfer and before NADH dissociation from the terminal E-NADH complex. The variation of activity of the enzyme with pH was studied. An enzyme group with pKa approx. 7.1 apparently promotes enzyme activity when in its alkaline form.
Dickinson
F M
FM
Department of Biochemistry, University of Hull, U.K.
Haywood
G W
GW
D000079:Acetaldehyde / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D009243:NAD / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013053:Spectrophotometry
D046911:Macromolecular Substances; D009243:NAD; D000444:Aldehyde Dehydrogenase; D000079:Acetaldehyde; D011188:Potassium