Glucose-6-phosphatase reactions catalyzed

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)... 

Hass and Byrne 28-30) and Segal (31) described in 1959 and 1960 the ability of liver microsomal glucose-6-phosphatase to catalyze an exchange reaction involving transphosphorylation between glucose-6-P and 14C-glucose [reaction (2a)]. The former workers (30) demonstrated that... 

Glucose is formed by hydrolysis of glucose 6-phosphate in a reaction catalyzed by glucose 6-phosphatase. 

Another reaction to which this method has been applied is the hydrolysis of glucose-1-phosphate catalyzed by the enzyme alkaline phosphatase. In this case the reaction might involve the breaking of either the C—O or the P—O bond. The reaction was caused to occur in water which had been enriched in The labeled... 

As discussed briefly in Section I,A, glucose-6-phosphatase is now known to be a multifunctional enzyme capable of catalyzing potent phosphotransferase as well as phosphohydrolase reactions [see Eqs. (1)—(4) ]. Compounds demonstrated to function as effective phosphoryl donors include fructose-6-P (30), mannose-6-P (40), PPi (35-38), a variety of nucleosidetriphosphates and nucleosidediphosphates—most effectively CTP, CDP, deoxy-CTP, ATP, ADP, GTP, GDP, and ITP (41, 45)— carbamyl-P (43), phosphoramidate (44), phosphopyruvate (42, 43) and glucose-6-P itself (30, 31). The various phosphoryl donors are also hydrolyzed by action of the enzyme (see preceding references). Eqqa-tions (1)—(4), which describe these various activities, are given in Section I,A. 

Enzymes often are known by common names obtained by adding the suffix -ase to the name of the substrate or to the reaction that they catalyze. Thus, glucose oxidase is an enzyme that catalyzes the oxidation of glucose glucose-6-phosphatase catalyzes the hydrolysis of phosphate from glu-cose-6-phosphate and urease catalyzes the hydrolysis of urea. Common names also are used for some groups of enzymes. For example, an enzyme that transfers a phosphate group from ATP to another molecule is usually called a kinase, instead of the more formal phosphotransferase. ... 

Fig. 1. Comparison of gluconeogenesis and glycolysis. The three steps of glycolysis that are irreversible are numbered. (1) Flexokinase in glycolysis is reversed by glucose 6-phosphatase in gluconeogenesis (2) PFK in glycolysis is reversed by fructose 1,6-bisphosphatase in gluconeogenesis (3) pyruvate kinase in glycolysis is reversed by two sequential reactions in gluconeogenesis catalyzed by pyruvate carboxylase and PEP carboxykinase.

Describe a possible means for the cytochemical detection and localization of the enzyme glucose 6-phosphatase it exists in liver and catalyzes the following reaction ... 

Figure 7.6. The metabolic reactions involved in the conversion of glycerol to glucose, the required precursor in the formation of sophorose. Note Reaction 1 catalyzed by triose phosphate isomerase. Reaction 2 catalyzed by aldolase. Reaction 3 catalyzed by fructose 1,6-bisphosphatase. Reaction 4 catalyzed by phosphoglucose isomerase., Reaction 6 catalyzed by glucose 6-phosphatase.

Sucrose phosphate synthetase catalyzes the reaction of UDP-glucose with fructose-6-P to form sucrose-6-P and UDP. This step is the penultimate step in the synthesis of sucrose in leaves. The chromatographic method can be applied to many UDP-glucose-requiring enzymes. The method eliminates the need for treatment of reaction mixtures with alkaline phosphatase. 

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