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Anthony Daniele
Chloramphenicol Acetyltransferase Type III
Chloramphenicol acetyltransferase type III (CAT III) is an enzyme which catalyzes the transfer of acetyl from acetyl-CoA to hydroxyl groups of chloramphenicol. CAT III is a trimeric protein
Introduction
Reaction of CAT III
In the first step of the reaction, Histidine-156 abstracts a proton from the 3-hydroxyl of chloramphenicol, causing a nucleophilic attack from the deprotonated oxygen onto the thioester bond of the acetyl-CoA. The 3-acetylchloramphenicol intermediate then rearranges, non-enzymatically, to a 1-acetylchloramphenicol intermediate. CAT III then causes another acetylation of the now regenerated 3-hydroxyl and 1,3-diacetylchloramphenicol is produced.