Question

Can someone please help I cannot understand this at all.

Question EN NHL Many antibiotics are inactivated by bacteria through acetylation, in which an acetyl group is transferred from a donor to a free amine (N-acetylation) or a free alcohol (O- acetylation). For instance, some resistant strains of Stapylococcus aureus possess an enzyme that transfers an acetyl group from acetyl-CoA (see your textbook for structure) to the amine attached to the exocyclic carbon of the antibiotic neamine. NH, OH OH The mechanism of the reaction is as follows: Neamine and acetyl CoA both bind, although it does not matter in which order. An active site aspartate is proposed to act as a general base on the neamine amine. Once activated, this amine attacks the carbonyl carbon of the acetyl group of acetyl-CoA, ultimately breaking the thioester bond to produce a free thiol (COASH). Although it is not yet known which active site residue acts as a general acid to protonate the leaving group, one possibility is that the above mentioned aspartate plays a dual general acid/general base role. Draw the active site and show how the mechanism works, assuming the dual role for the aspartate. You will need to draw 2 or 3 different active site "snap-shots" to show the entire process. (Note: you do not need to draw the entire structure of acetyl CoA). Be sure to clearly show the transition state (Note thioesters break in manner very similar to amides and regular esters).

Answer 1

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