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Contents 1 Chloramphenicol Acetyltransferase Type III 1.1 Introduction 1.1.1 Reaction of CAT III 1.2 Structure 1.3 References

Chloramphenicol Acetyltransferase Type III

Chloramphenicol acetyltransferase type III (CAT III) is an enzyme which catalyzes the transfer of an acetyl group from acetyl-CoA to hydroxyl groups of chloramphenicol. CAT III is a trimeric protein of about 25 000 k-Da.

Introduction

The bacterial enzyme CAT III

Reaction of CAT III

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In the first step of the reaction, Histidine-195 abstracts a proton from the 3-hydroxyl of chloramphenicol, promoting a nucleophilic attack from the deprotonated oxygen to the thioester bond of the acetyl-CoA. The intermediate produced, 3-acetylchloramphenicol, then rearranges non-enzymatically to 1-acetylchloramphenicol. Regeneration of the 3-hydroxyl allows another CAT III catalyzed nucleophilic attack to another acetyl-CoA and a 1,3-diacetylchloramphenicol product is formed. ^[1]

Structure

spinqualitylabelsall models PDB ID 4CLA Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

References

1. ↑ Murray IA, Lewendon A, Williams JA, Cullis PM, Shaw WV, Leslie AG. Alternative binding modes for chloramphenicol and 1-substituted chloramphenicol analogues revealed by site-directed mutagenesis and X-ray crystallography of chloramphenicol acetyltransferase. Biochemistry. 1991 Apr 16;30(15):3763-70. PMID:2015231

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