Effect of phosphate residue of NADPH on the interaction between catalytic domains of a multifunctional polyketide synthetic enzyme 6-hydroxymellein synthase
Association of NADPH with the ketoreducing domain of 6-hydroxymellein synthase, a multifunctional polyketide synthetic enzyme of carrot, evoked the alternation of microstructure around the primary binding site of the co-substrates acetyl- and malonyl-CoAs, and this resulted in the marked decrease in Km value of the enzyme protein for acetyl-CoA. In contrast, the enzyme did not show the increase in the affinity to the substrate when NADPH was replaced by NADH. These results suggest that the phosphate residue attached to 2'-position of adenosyl moiety of NADPH molecule plays an important role in the co-operative interaction between these functional domains of the synthase. Copyright 1998 Elsevier Science B.V.
Kurosaki
F
Cell Biology Laboratory, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-01, Japan