Phosphorylation and dephosphorylation of polyhydroxy compounds by class A bacterial acid phosphatases.
Nonspecific acid phosphatases share a conserved active site with mammalian glucose-6-phosphatases (G6Pase). In this work we examined the kinetics of the phosphorylation of glucose and dephosphorylation of glucose-6-phosphate (G6P) catalysed by the acid phosphatases from Shigella flexneri (PhoN-Sf) and Salmonella enterica (PhoN-Se). PhoN-Sf is able to phosphorylate glucose regiospecifically to G6P, glucose-1-phosphate is not formed. The K(m) for glucose using pyrophosphate (PPi) as a phosphate donor is 5.3 mM at pH 6.0. This value is not significantly affected by pH in the pH region 4-6. The K(m) value for G6P by contrast is much lower (0.02 mM). Our experiments show these bacterial acid phosphatases form a good model for G6Pase. We also studied the phosphorylation of inosine to inosine monophosphate (IMP) using PPi as the phosphate donor. PhoN-Sf regiospecifically phosphorylates inosine to inosine-5'-monophosphate whereas PhoN-Se produces both 5'IMP and 3'IMP. The data show that during catalysis an activated phospho-enzyme intermediate is formed that is able to transfer its phosphate group to water, glucose or inosine. A general mechanism is presented of the phosphorylation and dephosphorylation reaction catalysed by the acid phosphatases. Considering the nature of the substrates that are phosphorylated it is likely that this class of enzyme is able to phosphorylate a wide range of hydroxy compounds.
Tanaka
Naoko
N
Institute for Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 129, The Netherlands.
Hasan
Zulfiqar
Z
Hartog
Aloysius F
AF
van Herk
Teunie
T
Wever
Ron
R
Sanders
Robert-Jan
RJ
D000135:Acid Phosphatase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D044646:Ascophyllum / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D019298:Glucose-6-Phosphate / Q000378:metabolism*; D007288:Inosine / Q000378:metabolism*; D007291:Inosine Monophosphate / Q000378:metabolism*; D007700:Kinetics; D010755:Organophosphates / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019779:Salmonella enterica / Q000201:enzymology; D012763:Shigella flexneri / Q000201:enzymology; D013237:Stereoisomerism
D004791:Enzyme Inhibitors; D010755:Organophosphates; D011994:Recombinant Proteins; D007291:Inosine Monophosphate; D019298:Glucose-6-Phosphate; D007288:Inosine; D010544:Peroxidases; D010770:Phosphotransferases; D000135:Acid Phosphatase; D005947:Glucose