Choose the most plausible mechanism by which DON inhibits these enzymes. A) The
ID: 516555 • Letter: C
Question
Choose the most plausible mechanism by which DON inhibits these enzymes.
A) The diazomethyl group on carbon no. 5 in this glutamine analog is reactive and is thought to alkylate the position in the enzyme that becomes amidated by glutamine amidotransferase reactions. This irreversibly blocks access to the site by glutamine. B) 6-Diazo-5-oxonorleucine binds to allosteric centers of these enzymes altering the overall conformation of enzyme proteins, which ultimately distorts their active centers and diminishes their catalytic properties. C) DON interacts with hydrophobic amino acid side chains inside protein molecules because of its amphiphilic properties. This destabilizes the structure of the enzymes depriving them of their native function as catalysts. D) The overall molecular structure of DON resembles that of glutamine, but the presence of electrically-charged diazomethyl group on carbon no. 5 leads to much more tight binding of DON to the enzymes substrate-binding center. This leads to displacement of glutamine from the substrate-binding center and consequently decreases the reaction rate.Explanation / Answer
The answer A. The diazomethyl group on carbon no. 5 in this glutamine analog is reactive and is thought to alkylate the position in the enzyme that becomes amidated by glutamine amidotransferase reactions. This irreversibly blocks access to the site by glutamine.
DON is 6-Diazo-5-oxo-L-norleucine, it's structure of resembles that of glutamine. It covalently binds with the active site of the enzyme and interacts with residues amino acids. DON releases the diazo group (N2) from the inhibitor and results in the formation of an enzyme-inhibitor complex by the nucleophilic attack of active site.