7-methyl-6-Thioguanosine is a chromophoric substrate that is used to quantify inorganic phosphate (Pi). In the presence of purine nucleoside phosphorylase, it reacts with Pi to produce 7-methyl-6-thioguanine and ribose 1-phosphate, with the increase in 7-methyl-6-thioguanine followed by continuous spectrophotometry at an absorbance of 355-360 nm.1 7-methyl-6-Thioguanosine is also used to measure changes in Pi levels in coupled enzyme systems, including assays of the activities of protein phosphatases, phosphorylase kinases, GTPases, and ATPases.1,2,3,4
1.Webb, M.R.A continuous spectrophotometric assay for inorganic phosphate and for measuring phosphate release kinetics in biological systemsProc. Natl. Acad. Sci. USA89(11)4884-4887(1992) 2.Cheng, Q., Wang, Z.X., and Killilea, S.D.A continuous spectrophotometric assay for protein phosphatasesAnal. Biochem.310(2)156-162(2002) 3.Wang, Z.X., Cheng, Q., and Killilea, S.D.A continuous spectrophotometric assay for phosphorylase kinaseAnal. Biochem.230(1)55-61(1995) 4.Tan, Y.C., Wu, W.N., Zheng, Y., et al.Characterization of the interactions between the small GTPase RhoA and its guanine nucleotide exchange factorsAnal. Biochem.310(2)156-162(2014)