Pyrophosphate phosphohydrolase

Inorganic diphosphatase. Pyrophosphate phosphohydrolase. Diphosphate phosphohydrolase. 

There is similar ambiguity in the case of inorganic pyrophosphatase (pyrophosphate phosphohydrolase, EC 3.6.1.1). We had reported that this enzyme appeared to function as an ecto-enzyme in some cultured cells (REICHERT jet, 1974) and similar observations were made elsewhere (STEFANOVIC > 1975a), but the findings... 

PHOSPHATIDYLGLYCEROL PHOSPHATE PHOSPHOHYDROLASE PHOSPHOENOLPYRUVATE CARBOXYKI-NASE (PYROPHOSPHATE)... 

In reaction (1), which is catalyzed by a phosphohydrolase, or as it is more commonly called, an ATPase, the jS/y-phosphoanhydride bond of the ATP is cleaved, with the result that ADP and inorganic phosphate (Pj) are formed. Reaction (2), catalyzed by a pyrophosphohydrolase, cleaves the a,f.3 bond of the ATP, with the result that AMP and pyrophosphate (PR) are formed. Finally, (3) is the well-known reaction catalyzed by adenylate kinase, or myoki-nase, where ATP and AMP react to form two ADP molecules. Since reaction... 

Mammalian diphosphoinositol polyphosphate phosphohydrolases ( DIPPs, Figure 1 bottom left) have been identified that cleave Ins pyrophosphates back to Ins P6 (Caffrey et al., 2000 Hidaka et al., 2002 Hua et al., 2003 Safrany et al., 1998). However Ins P6 kinases can act in the reverse direction, utilizing Ins pyrophosphates as phosphate donor to regenerate ATP from ADP (Huang et al., 1998), whereas DIPPS act only in Ins pyrophosphate breakdown. 

Nucleosidediphosphatase [Nucleosidediphosphate phosphohydrolase] (3.6.1.6) is produced and catalyzes the reaction A nucleoside diphosphate + H2O = a nucleotide + orthophosphate. [Acts on IDP, GDP, UDP and also on D-ribose 5-diphosphate.] Nucleotide pyrophosphatase [Dinucleotide nucleotidohydrolase] (3.6.1.9) is produced and catalyzes the reaction A dinucleotide + H2O = 2 mononucleotides. [Substrates include NAD" " NADP ", FAD, CoA and also ATP and ADP.] Deoxycytidinetriphosphatase [dCTP nucleotidohydrolase, Deoxy-CTPase, dCTPase] (3.6.1.12) is produced and catalyzes the reaction dCTP + H2O = dCMP + pyrophosphate. [Also hydrolyses dCDP to dCMP and orthophosphate]... 

The dependence of glucoso-6-phosphatase activity upon its interaction with membranes has been clearly demonstrated. This enzyme is located on the membranes of the smooth and rough endoplasmic reticulum and remains associated with isolated microsomes. This multifunctional enzyme demonstrated glucoso-6-phosphohydrolase activity (hydrolase) and pyrophosphate glucosophosphotrans-ferase activity (transferase) ... 

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