Abstract
A rapid and convenient chemical assay for the enzyme d-glucose 6-phosphate–1l-myoinositol 1-phosphate cyclase is described. The 1l-myoinositol 1-phosphate formed enzymically was oxidized with periodic acid liberating inorganic phosphate, which was assayed. myoInositol 2-phosphate can be assayed in the same way. Glucose 6-phosphate and other primary phosphate esters gave only very small quantities of inorganic phosphate under the conditions described. The Km of the enzyme for d-glucose 6-phosphate, 7.5±2.5×10−4m, was identical with that measured by the radiochemical method. 2-Deoxy-d-glucose 6-phosphate was a powerful competitive inhibitor, Ki 2.0±0.5×10−5m, but was not a substrate for the enzyme.
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Selected References
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- Barnett J. E., Corina D. L. The mechanism of glucose 6-phosphate-D-myo-inositol 1-phosphate cyclase of rat testis. The involvement of hydrogen atoms. Biochem J. 1968 Jun;108(1):125–129. doi: 10.1042/bj1080125. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eisenberg F., Jr D-myoinositol 1-phosphate as product of cyclization of glucose 6-phosphate and substrate for a specific phosphatase in rat testis. J Biol Chem. 1967 Apr 10;242(7):1375–1382. [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Piña E., Tatum E. L. Inositol biosynthesis in Neurospora crassa. Biochim Biophys Acta. 1967 Mar 22;136(2):265–271. doi: 10.1016/0304-4165(67)90071-2. [DOI] [PubMed] [Google Scholar]
- Ruis H., Molinari E., Hoffmann-Ostenhof O. Untersuchungen über die Biosynthese der Cyclite. XIX. Uber ein D-Glucose-6-phosphat in L-1-O-Phospho-myo-inosit überführendes Enzym aus höheren Pflanzen. Hoppe Seylers Z Physiol Chem. 1967 Dec;348(12):1705–1706. [PubMed] [Google Scholar]
- Sherman W. R., Stewart M. A., Zinbo M. Mass spectrometric study on the mechanism of D-glucose 6-phosphate-L-myo-inositol 1-phosphate cyclase. J Biol Chem. 1969 Oct 25;244(20):5703–5708. [PubMed] [Google Scholar]