Muscle phosphoglucomutase

In three cases, a n-glucose-producing amylase was absent. In one case, muscle phosphoglucomutase activity was only 5% of normal, and subsequent glycolysis was 25% of normal. ... 

P9. Postemak, T., and Rosselet, J. P., Action de la phosphoglucomutase du muscle sur des acides aldose-l-phosphoriques. Transformation de l acide galactose-l-phos-phorique. Helv. Chim. Acta 37, 246-250 (1954). 

Phosphoglucomutase (EC 2.7 5.l) slowly converts R-l-P to ribose-5-phosphate. A mixture of 35 mM R-l-f O J-P, 17mM R-l-[ L 0l(]-P and less than lmg glucose-1,6-diphosphate at pH 7 33 was equilibrated with phosphoglucomutase (Sigma, P3397, rabbit muscle), at 25°C for 3 Hr. The 31p NMR spectrum was recorded at pH 7 37- The enzyme converted ca. 20 to a mixture of ribose-5-phosphate l Ol (resonance identified by addition of authentic material) and I80I803 species. This demonstrated that the enzyme catalyzed formation of the 0-P bond. 

Pig-kidney extracts have some phospho-iV-acetyl-D-glucosamine mutase activity. The ratio of phosphoglucomutase to phospho-AT-acetyl-n-glucos-amine mutase activity is 60 1 in these extracts. In rabbit muscle, this ratio i is 1200 1. Phosphoglucosamine mutase activity was not checked in any of the phosphomutase preparations investigated by this worker. 

II. 91%. A normal constituent of resting muscle, probably always existing in equilibrium with fructose-6-phosphate. For the enzymatic conversion from the I -phosphate see a -Glucose-1 -phosphate. Isoln from a crude mixture of hex -ose phosphates, obtained by yeast fermentation Robison, King, -Biochem. J. 25, 323 (1931). Prepn by the action of phosphoglucomutase on a-glucose-1 -phosphate Colowjck. Sutherland, J. Biol Chem. 144, 423 (1942) from acetone... 

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. 

Phosphoglucomutase (rabbit muscle, 50 U) UDP-glucose-pyrophosphorylase (bovine liver, 10 U) ... 

Klenow concluded that both phosphoglucomutase and phosphoiibomutase activities reside in a single protein the ratio of the two activities remained constant during purification of the enzyme from muscle, both activities were stimulated by Mg and cysteine, both exhibited the same pH optimum, and both were inhibited by inorganic anions. On the other hand, Guarino and Sable 26, 27) have purified a specific phosphoiibomutase from uterine muscle this mutase showed no requirement for divalent cations. At the present time, it is difficult to evaluate the relative physiological significance of the two mutases in the interconversion of the ribose phosphates. 

Triose Metabolism Glycogen Breakdown 16 Muscle Phosphorylase Liver Phosphorylase Phosphoglucomutase Amylo-1,6-glucosidase... 

These conclusions were based on advanced isotopic studies showing that if fructose-1 is converted to fructose-6-phosphate, it can go directly to glycogen through the isomerase and phosphoglucomutase reaction without first being split into trioses. Under those conditions, all the of the hexoses entering the glycogen molecule will be recovered in carbon 1, and this is precisely what happens in muscle. In liver, the label of the fructose-1 is randomized why this happens will become obvious when the pathway for fructose-1-phosphate has been outlined. 

The glucose 1-phosphate released by phosphorolysis is converted into glucose 6-phosphate by phosphoglucomutase. In muscle the glucose 6-phosphate enters the glycolytic sequence and is used for ATP production. 

Cori, Colowick, and Cori were the first to study the phosphoglucomutase reaction, and they demonstrated the widespread occurrence of this enzyme in animal tissues and in yeast. The muscle enzyme was finally crystallized by Najjar. Leloir and his co-workers proved the... 

---