Hi Seema, I guess the turnover number of the mutant enzyme is considerably low compared to the wild type one, as well as in the crystallization condition. It might be because the energy barrier of the transition state could be much higher for the mutant enzyme in the given crystallization condition compared to the wild type version.
Best, Sudipta. Sudipta Bhattacharyya Postdoctoral fellow, Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, USA. On Fri, May 26, 2017 at 3:48 PM, Seema H Irani <irani.se...@utexas.edu> wrote: > I crystallized a PLP dependent enzyme and wanted to capture the enzyme > substrate complex, however due high activity of the enzyme I could see no > density at the active site upon soaking with the substrate. I hence made a > bunch of mutants of the active site residues and one of them showed density > consistent with the substrate in some of the molecules in the asymmetric > unit. Surprisingly however when I measured the activity of this mutant it > had 30% of the wildtype activity I am wondering why is it still possible > for me to see substrate density for this mutant? > > >
