The Enzyme Database

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Accepted name: triphosphate—protein phosphotransferase
Reaction: triphosphate + [microsomal-membrane protein] = diphosphate + phospho-[microsomal-membrane protein]
Other name(s): diphosphate:microsomal-membrane-protein O-phosphotransferase (erroneous); DiPPT (erroneous); pyrophosphate:protein phosphotransferase (erroneous); diphosphate—protein phosphotransferase (erroneous); diphosphate:[microsomal-membrane-protein] O-phosphotransferase (erroneous)
Systematic name: triphosphate:[microsomal-membrane-protein] phosphotransferase
Comments: This enzyme was originally thought to use diphosphate as substrate [1] but this has since been disproved [2]. The activity is observed as the second part of a biphasic reaction after depletion of ATP. Tripolyphosphate is a contaminant of [γ-32P]ATP.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 74092-32-3
1.  Lam, K.S. and Kasper, C.B. Pyrophosphate:protein phosphotransferase: a membrane-bound enzyme of endoplasmic reticulum. Proc. Natl. Acad. Sci. USA 77 (1980) 1927–1931. [PMID: 6246514]
2.  Tsutsui, K. Tripolyphosphate is an alternative phosphodonor of the selective protein phosphorylation of liver microsomal membrane. J. Biol. Chem. 261 (1986) 2645–2653. [PMID: 3949741]
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