Figure 4.
NAAT activity of naat-A and naat-B expressed in the yeast. naat-A and naat-B were introduced into wild-type S. cerevisiae, and NAAT activity was determined from the amount of deoxymugineic acid detected with HPLC. The arrowhead indicates the retention time for deoxymugineic acid. A, Deoxymugineic acid as a standard; B, naat-A; C, naat-B; D, pYH23 (control). The specific activities (pkat mg−1 protein) of NAAT-A, NAAT-B, and pYH23 expressed in yeast are 0.36 ± 0.01, 0.13 ± 0.03, and not detected, respectively. Each value represents the mean of four replicates.