Methods for measuring activity of glutamine:fructose 6-phosphate amidotransferase and activity of inhibitors thereof

A method for measuring the inhibitory activity of a test compound on glutamine:fructose 6-phosphate amidotransferase, which comprises the steps of:

• (a) forming a mixture of a test compound, glutamine:fructose 6-phosphate amidotransferase, fructose 6-phosphate, and glutamine;
• (b) incubating the mixture in (a) under physiological conditions for a time sufficient to allow the test compound to inhibit glutamine:fructose 6-phosphate amidotransferase from forming glucosamine 6-phosphate;
• (c) acetylating the glucosamine 6-phosphate in (b) to form N-acetylglucosamine 6-phosphate;
• (d) reacting the N-acetylglucosamine 6-phosphate in (c) with Ehrlich's reagent;
• and (e) measuring the amount of N-acetylglucosamine 6-phosphate in (d) by determining the optical density at 500-610 nm of the mixture in (d) and comparing the amount of N-acetylglucosamine 6-phosphate in (d) with a control sample of glutamine:fructose 6-phosphate amidotransferase not containing the test compound and a control sample of N-acetylglucosamine 6-phosphate, thereby determining the inhibitory activity of the test compound.