A modified screening method for estimating erythrocyte glucose phosphate isomerase.

A fluorimetric method to estimate erythrocyte glucose phosphate isomerase is described. Five mul of blood is added to 100 mul of water. Ten mul of the resulting hemolysate is incubated with a reaction mixture (200 mul) containing Tris-HCl buffer pH 8.0, 20 mumoles, MgCl(2) 2 mumoles, nicotinamide adenine dinucleotide phosphate 0.08 mumoles, glucose-6-phosphate dehydrogenase 0.2 EU and fructose-6-phosphate 0.12 mumoles. After ten minutes of 25 degrees C 20 mul of the mixture is added to 2 ml of 0.01 M phosphate buffer pH 7.4 and the nicotinamide adenine dinucleotide phosphate fluorescence determined. Two ml of water was added to the remaining reaction mixture and the hemoglobin concentration determined at 410 nm. The technique is primarily designed for use with small amounts of blood, of widely varying activity, from various animal species.