Molecular Biology Of The Cell 6th Edition by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter

Exercise 5

A histidine side chain is known to play an import- ant role in the catalytic mechanism of an enzyme; how- ever, it is not clear whether histidine is required in its pro- tonated (charged) or unprotonated (uncharged) state. To answer this question you measure enzyme activity over a range of pH, with the results shown in Figure Q2-1. Which form of histidine is required for enzyme activity?