The catalytic effect of Mg2+ and imidazole on the decomposition of 5-phosphoribosyl-alpha-1-pyrophosphate in aqueous solution.
The rate of decomposition of aqueous solutions of 5-phosphoribosyl-alpha-1-pyrophosphate (PRPP) is greatly enhanced by the presence of certain divalent ions. High levels of Mg(2+) were shown to increase the rate of phosphate removal from PRPP by factors greater than 100-fold. The combined action of Mg(2+) and a nitrogenous compound (imidazole was employed in this study) increases the degradation rate constants by up to 1000-fold. The degradation of PRPP in neutral solutions follows two main paths, a pyrophosphate hydrolysis reaction yielding ribose 5-phosphate and an internal beta-phosphate cleavage yielding 5-phosphoribosyl-1,2 cyclic phosphate. The catalytic effect of Mg(2+) on PRPP degradation appears to suggest a connection between the observed rate enhancements and the dimagnesium form of PRPP. Rate enhancing effects of Mg(2+) are greatest at pH values (i.e. pH>7) which promote strong phosphate-Mg(2+) interaction.
Meola
Mark
M
Department of Chemistry, Plattsburgh State University, 101 Broad Street, Plattsburgh, NY 12901, USA.
Yamen
Brenda
B
Weaver
Kelly
K
Sandwick
Roger K
RK
D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology*; D010430:Pentosyltransferases / Q000737:chemistry; D010754:Phosphoribosyl Pyrophosphate / Q000737:chemistry / Q000378:metabolism*; D012996:Solutions
D007093:Imidazoles; D012996:Solutions; D010754:Phosphoribosyl Pyrophosphate; C029899:imidazole; D010430:Pentosyltransferases; D008274:Magnesium