Exchange reactions phosphorylating enzyme

Linear enzyme concentration dependence is observed for both the phosphorylation and exchange reaction over a 1000-fold enzyme concentration range, pM to nM, if the reactions are run in 25 mM Tris, 5mM Mg, pH 7.6. Under these conditions, the enzyme is associated. 

This enzyme [EC 3.1.3.9] catalyzes the hydrolysis of o-glucose 6-phosphate to yield o-glucose and orthophosphate. Some glucose phosphatases also catalyze transphosphorylation reactions from carbamoyl phosphate, hexose phosphates, pyrophosphate, phosphoenolpyru-vate and nucleoside di- and triphosphates, using D-glu-cose, D-mannose, 3-methyl-D-glucose, or 2-deoxy-D-glu-cose as phosphoryl acceptors. See Isotope Exchange (Reactions Away from Equilibrium)... 

Saier, M.H. Schmidt, M.R. Lin, P. Phosphoryl exchange reaction catalyzed by enzyme I of the bacterial phosphoenolpyruvate sugar phosphotransferase system. Kinetic characterization. J. Biol. Chem., 255, 8579-8584 (1980)... 

Most kinases transfer chiral phospho groups with inversion and fail to catalyze partial exchange reactions that would indicate phosphoenzyme intermediates. However, nucleoside diphosphate kinase contains an active site histidine which is phosphorylated to form a phosphoenzyme.869 The enzyme catalyzes phosphorylation of nucleoside diphosphates other than ADP by a nucleotide triphosphate, usually ATP. 

These exchange reactions can support the existence of a double-displacement mechanism via a covalent intermediate if cosubstrates are absent. Reaction (19a) could proceed if ATP phosphorylates the enzyme and the phosphoryl group is... 

S Additional information <2> (<2> the enzyme catalyzes an exchange reaction in which a phosphoryl moiety is transferred from one molecule of the heat stable phosphocarrier protein Hpr to another [7]) [7]... 

NEM <2> (<2> inhibits phosphoenol-dependent phosphorylation of mannitol and mannitol 1-phosphate, no effect on activity of exchange reaction [7] <2> enzyme reconstituted in phospholipid vesicles [11]) [7, 11]... 

The detection and characterization of intermediates in complex reactions is often accomplished through the use of isotope-exchange studies. In the case of enzymic phosphoryl transfer reactions, the presence of a phosphorylated enzyme intermediate is implicated by a partial exchange process as exemplified by the following reaction of hexokinase (Knowles, 1980) ... 

Many people try to reconstruct the steps of oxidative phosphorylation by studying the exchange reactions outlined above. These reactions were described first in intact mitochondria, and later in mitochondrial fragments obtained by treating the organelle with digi-tonin or ultrasound. The enzymes involved have occasionally been prepared in a soluble form. 

The prosthetic group associated with the molybdenum atom of the molybdenum cofactor found in most molybdenum-containing enzymes except nitrogenase (See Molybdenum Cofactor). Many of these enzymes catalyze two-electron redox reactions involving the net exchange of an oxygen atom between the substrate and water. In bacterial enzymes a nucleotide is linked to the phosphoryl group. 

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