Fig. 3

Protein engineering of ALAS for deregulation of heme inhibition. A The l-Cysteine residues in ALAS (PDB ID: 7X98). The C51, C75, C132, C200, C263, and C340 residues in the protein structure are indicated in blue. B The specific activities and residual activities of wild-type ALAS and its mutants with or without adding 2.5 µM hemin. Residual activity was determined after incubating the enzyme with 2.5 µM hemin at 37 ℃ for 1 h. Residual activity was reported as a percentage of the activity measured without hemin. C The residual activities of wild-type ALAS and its mutants with hemin (0 µM to 10 µM). D The UV–Vis spectra of the mixture of 20 µM hemin and 10 µM ALAS. The mixture was chilled on ice for 1 h and used for full-wavelength scanning. Data are presented as mean values +/− SD (n = 3 independent experiments)