Describe why Histidine is often found in active sites and is involved in the catalytic mechanisms...

Describe why Histidine is often found in active sites and is involved in the catalytic mechanisms of enzymes. What role does it generally play in catalytic mechanisms? Draw an example of a catalytic mechanism that involves Histidine as a critical amino acid residue.

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Expert Solution

Histidine has an imidazole ring which can be protonated and deprotonated depending on the physiological pH. So, it can perform different roles in catalysis. Its pKa is 6 so it can be protonated and deprotonated very easily at physiological pH. When protonated it acts as a proton donor (acid) and when it is deprotonated it acts as a proton acceptor (base). Histidine also acts as electron donor (lewis base) to act as ligand for a metal ion for the metalloenzymes.

Reaction involving histidine: Protons are transferred from serine to histidine. Here histidine acts as a base.

gladiator answered 1 year ago

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