A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction. If the pK_aof the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2, what is likely the primary role of histidine in the catalytic reaction? A) acts as a proton donor B) forms a covalent bond with the substrate C) stabilizes a charged intermediate D) reduces the entropy of the substrate

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Quizplus · Accepted Answer

At a pH of 7.2, which is above the pKa of 6.5, histidine is likely to be deprotonated and can act as a proton donor in the catalytic reaction.

A Histidine Was Determined to Be the Critical Residue Involved