Kinetic analysis of recombinant HDR1 and HDR2 enzymes of Populus × canescens and Picea abies. Lineweaver-Burk plots depict data obtained from in vitro assays of heterologously expressed recombinant HDR1 and HDR2 enzymes of poplar A) and spruce B). While the lines of the HDR2 measurements show similar slopes and intercepts indicating similar kinetics in both species, HDR1 showed major differences between poplar and spruce as seen in the K_m- and k_cat values for the respective enzymes C). The ratio of DMADP to IDP is similar for three of the four enzymes, but PaHDR1 shows a remarkable increase in IDP production. Each data point represents the mean of two technical replicates from each of two separate experiments.