Purification and Properties of Nicotinamide Adenine Dinucleotide Phosphate-specific Benzaldehyde Dehydrogenase from Pseudomonas

The NADP-specific benzaldehyde dehydrogenase (benzaldehyde-NADP oxidoreductase, EC 1.2.1.7) of Pseudomonas fluorescens , strain A.3.12, has been purified 80- to 90-fold and found to have a molecular weight of approximately 200,000. The reaction shows optimal activity at pH 8.5. Univalent cations such as K + , Rb + , and NH 4 + activate the enzyme. The K m for benzaldehyde is 0.2 µ m , and that of NADP was calculated to be 37 µ m . Enzymatic activity was extremely sensitive to sulfhydryl reagents such as p -hydroxymercuribenzoate and N -ethylmaleimide. Only the coenzyme NADP offered protection against and inhibition by these reagents. The enzyme was completely inactivated after heating for 5 min at 50°, whereas in the presence of 1.0 m m NADP only 8% of the catalytic activity was lost after 5 min.