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O. O. O. OH O. OH OH. OH OH. A model of the active site of Amidophosphoribosyltransferase. N-terminal nucleophile. Glnase. Glnase. Glnase. + H 3 N. + H 3 N. COO -. O. O. COO -. H. S. S. H 2 N. H 2 N+. O. O. NH 3. H 2 N. H. G. PRTase. PRTase. PRTase. Pi.
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O O O OH O OH OH OH OH A model of the active site of Amidophosphoribosyltransferase N-terminal nucleophile Glnase Glnase Glnase + H3N + H3N COO- O O COO- H S S H2N H2N+ O O NH3 H2N H G PRTase PRTase PRTase Pi Pi Pi O- O- O O P P O O O O O O H O PRTase P P O P O- O O- O- O- O- O- O A O P “A” Site O OH OH “A” Site “A” Site Before reaction (substrates bound) NH3 Channeling Feedback Inhibition by ADP+ GMP