Enzymes phosphoglucomutase

Details of the breakdown are presented in Appendix 6.4. The glucose 1-phosphate is converted to glucose 6-phosphate by the action of the enzyme phosphoglucomutase. The glucose 6-phosphate is then metabohsed by glycolysis. 

As an example, let s make a simple calculation of the standard free-energy change of the reaction catalyzed by the enzyme phosphoglucomutase ... 

The enzyme phosphoglucomutase catalyzes the interconversion of glucose-1-phosphate and glucose-6-phosphate (fig. 12.17). The interconversion occurs in two discrete steps by way of a phosphorylated enzyme and glucose-1,6-bisphos-phate. The reactions are... 

Fig. 6.9. Electrophoretic patterns obtained with soluble extracts of protoscoleces removed from hydatid cysts of human(H), camel(C), sheep(S), cattle(B) and goat(G) origin from Kenya. Upper panel stained for the enzyme glucose phosphate isomerase lower panel stained for the enzyme phosphoglucomutase. (Reprinted with permission from International Journal for Parasitology, 12, Macpherson, C. N. L. McManus, D. P., A comparative study of Echinococcus granulosus from human and animal hosts in Kenya using isoelectric focusing and isoenzyme analysis, 1982, Pergamon Journals Ltd.)...

The involvement of methionine sulfonium salts in these chemical cleavage reactions may stimulate experiments to show the significance of special methionine residues in the active centers and the catalytic sites of enzymes. Such an important role for a particular methionine has been postulated for the enzymes phosphoglucomutase and chymotrypsin on the basis of photooxidation studies (Ray et al., 1960). 

Glucose 1-phosphate released from glycogen can be readily converted into glucose 6-phosphate (Section 21.1.3k an important metabolic intermediate, by the enzyme phosphoglucomutase. 

G6P is a phosphorylated form of glucose commonly found in cells. G6P is an intermediate in glycolysis, gluconeogenesis, the pentose phosphate pathway, the Calvin Cycle, glycogen biosynthesis, glycogen breakdown, and sugar interconversion. The latter three pathways indirectly involve G6P via the enzyme phosphoglucomutase. 

The enzyme phosphoglucomutase catalyzes the interoonversion of glucose-1-phosphate and giucose-6-phosphate,... 

Glucose-l-P04 is converted to glucose-6-P04 by the enzyme phosphoglucomutase, and can be dephosphorylated in the liver to enter the blood stream for distribution. In muscle cells, it goes directly into glycolysis. 

When the glucose originates by breakdown of its polymeric forms, starch or glycogen, it is already phosphorylated, as glucose-1-phosphate, and the initial reaction is catalyzed by the enzyme phosphoglucomutase. 

Identification of the intermediate form of the enTyme the enzyme phosphoglucomutase catalyses the conversion of glucose 1-phosphate to glucose 6-phosphate. Phosphoserine has been identified in this enzyme to demonstrate that serine participates as the intermediate phosphate acceptor. 

In this laboratory two enzymes, phosphoglucomutase and a UDP-glucose pyrophosphorylase, have been demonstrated in cell free extracts of S. niveus (BC-345) which could catalyze the initial steps necessary in the reaction mechanism described above. In the pyrophosphorylase reaction, no other nucleotide triphosphate tested (TTP, CTP, GTP or ATP) would substitute for uridine triphosphate (UTP). The possible involvement of UDP-glucose in the formation of the noviose moiety of novobiocin is currently being studied in this laboratory. 

For example in sucrose synthesis, glucose-6-phosphate produced by the action of G-6-P isomerase on fructose-6-P, an intermediate in the carbon reduction cycle, is converted to glucose-1-phosphate by the enzyme phosphoglucomutase. This compound can then combine with the nucleotide, uridine triphosphate (UTP) to produce... 

It is known that certain cell constituents are involved in the reversible activation and inactivation of enzymes. Thus, the enzyme phosphoglucomutase which catalyses the reaction... 

---