Phosphoglucomutase ribose phosphate

Phosphoglucomutase acts not only on D-glucose and D-mannose phosphates (see p. 204) but also on D-ribose phosphates, the interconversion of D-ribosyl phosphate and D-ribose 5-phosphate being similarly accelerated by D-glucose 1,6-diphosphate,193 which appears to generate D-ribose 1,5-diphos-phate as cofactor.199(a) (b) (o) D-Ribose 5-phosphate is formed from D-ribose and ATP in the presence of yeast ribokinase.m... 

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. 

Only catalytic amounts of the diphosphates are required for the reaction. The phosphoglucomutase also acts on D-mannose phosphate and D-ribose phosphate and is thought to catalyze the interconversion of D-mannose 1-phosphate to D-mannose 6-phosphate and D-ribose 1-phosphate to D-ribose... 

The results of that experiment allow one to synthesize a-D-ribose-l-[l80U]-phosphate which can be employed to determine the position of bond cleavage by other enzymes whose role is transfer of phosphate (Pj) to water or to another acceptor. We report results on a. the position of bond cleavage in R-l-P by PNP from human erythrocytes and E. coli as well as by alkaline phosphatase, acid phosphatase, formic acid andb. the position of bond making in ribose-5-phosphate by phosphoglucomutase. The earlier experiment from this laboratory employed the equilibration ... 

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. 

In contrast to phosphohydrolases, the phosphatase activity of enzymes which non-hydrolytically catalyse the transfer of phosphate groups can be stimulated by vanadate. Vanadate can spontaneously form esters with unphosphorylated substrates such as sugars. These vanadate esters act as alternative substrates for mutases and isomerases, stimulating their phosphatase activity. Examples are phosphoglucomutase, which catalyses the mutation (phosphate shift) between glucose-1-phosphate and glucose-6-phosphate, and phosphoribose isomerase, which catalyses the isomerisation between ribose-5-phosphate and ribulose-5-phosphate.P ]... 

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