Glucose diphosphate assay

In the presence of excess phosphohexose isomerase and glucose-6-phos-phate dehydrogenase the rate of reduction of TPN is proportional to the rate of cleavage of fructose diphosphate. For cases when small, quantities of fructose diphosphate must be used, a second spectrophoto-metric assay, in which fructose diphosphate is regenerated, has been proposed 20). Fructose 6-phosphate is phosphorylated with ATP and phosphofructokinase, and the adenosine diphosphate (ADP) produced is measured with phosphoenolpyruvate and lactic dehydrogenase ... 

Recently, a universal enzyme-coupled fluorescence assay for glycosyl transferases was developed. This method is extremely cost-effective and is based on the quantification of nucleotides produced in the glycosyl transfer reaction. The guanosine diphosphate (GDP), uridine diphosphate (UDP), and cytidine monophosphate (CMP) are phos-phorylated with nucleotide kinase in the presence of excess of ATP, generating ADP. Via coupled enzyme reactions involving ADP-hexokinase,glucose-6-phosphate dehydrogenase, and diaphorase, the ADP is utilized for the conversion of resazurin to resorufin, which is then quantified by fluorescence measurement. 

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