Publications

• D-ribose-5-phosphate isomerase B from Escherichia coli is also a functional D-allose-6-phosphate isomerase, while the Mycobacterium tuberculosis enzyme is not.

  Roos A.K., Mariano S., Kowalinski E., Salmon L., Mowbray S.L.

  Interconversion of D-ribose-5-phosphate (R5P) and D-ribulose-5-phosphate is an important step in the pentose phosphate pathway. Two unrelated enzymes with R5P isomerase activity were first identified in Escherichia coli, RpiA and RpiB. In this organism, the essential 5-carbon sugars were thought t ... >> More

  Interconversion of D-ribose-5-phosphate (R5P) and D-ribulose-5-phosphate is an important step in the pentose phosphate pathway. Two unrelated enzymes with R5P isomerase activity were first identified in Escherichia coli, RpiA and RpiB. In this organism, the essential 5-carbon sugars were thought to be processed by RpiA, while the primary role of RpiB was suggested to instead be interconversion of the rare 6-carbon sugars D-allose-6-phosphate (All6P) and D-allulose-6-phosphate. In Mycobacterium tuberculosis, where only an RpiB is found, the 5-carbon sugars are believed to be the enzyme's primary substrates. Here, we present kinetic studies examining the All6P isomerase activity of the RpiBs from these two organisms and show that only the E. coli enzyme can catalyze the reaction efficiently. All6P instead acts as an inhibitor of the M. tuberculosis enzyme in its action on R5P. X-ray studies of the M. tuberculosis enzyme co-crystallized with All6P and 5-deoxy-5-phospho-D-ribonohydroxamate (an inhibitor designed to mimic the 6-carbon sugar) and comparison with the E. coli enzyme's structure allowed us to identify differences in the active sites that explain the kinetic results. Two other structures, that of a mutant E. coli RpiB in which histidine 99 was changed to asparagine and that of wild-type M. tuberculosis enzyme, both co-crystallized with the substrate ribose-5-phosphate, shed additional light on the reaction mechanism of RpiBs generally. << Less

  J. Mol. Biol. 382:667-679(2008) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Pentose phosphate isomerase and epimerase from animal tissues.

  DICKENS F., WILLIAMSON D.H.

  Biochem J 64:567-578(1956) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Spinach phosphoribulokinase.

  HURWITZ J., WEISSBACH A., HORECKER B.L., SMYRNIOTIS P.Z.

  J Biol Chem 218:769-783(1956) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Two ribose-5-phosphate isomerases from Escherichia coli K12: partial characterisation of the enzymes and consideration of their possible physiological roles.

  Essenberg M.K., Cooper R.A.

  Two physically and genetically distinct forms of ribosephosphate isomerase have been identified in Escherichia coli K12. The constitutive ribosephosphate isomerase A has a Km for ribose 5-phosphate (4.4 +/-0.5 mM) six times greater than that of the inducible ribosephosphate isomerase B (0.83 +/-0. ... >> More

  Two physically and genetically distinct forms of ribosephosphate isomerase have been identified in Escherichia coli K12. The constitutive ribosephosphate isomerase A has a Km for ribose 5-phosphate (4.4 +/-0.5 mM) six times greater than that of the inducible ribosephosphate isomerase B (0.83 +/-0.13 mM). Treatment of the enzymes with 1.25 mM iodoacetate resulted in 100% loss of activity for ribosephosphate isomerase B, whereas ribosephosphate isomerase A was unaffected. Various cellular metabolites were tested and found to be without significant effect on either enzyme. The two enzymes could be separated by filtration on Sephadex G75 superfine and their apparent molecular weights were 45000 for ribosephosphate isomerase A and 32000-34000 for ribosephosphate isomerase B. Under certain conditions the two enzymes showed different patterns of heat inactivation but the results with ribosephosphate isomerase A varied in an unusual way with the protein concentration. Ribosephosphate isomerase B was formed inducibly in a mutant lacking ribosephosphate isomerase A but there was no evidence for the production of ribosephosphate isomerase B in wild-type cells. The formation of ribosephosphate isomerase B was not a consequence of the ribosephosphate isomerase B mutation, since strains could be constructed which formed both enzymes constitutively in the anticipated amounts. The ribosephosphate isomerase formed by a secondary mutant obtained from a ribosephosphate-isomerase-A-negative strain was identified as ribosephosphate isomerase B on the basis of its Km, elution profile from Sephadex G75, inhibition of iodoacetate, and heat inactivation. The ribosephosphate isomerases of another Escherichia coli K12 strain, X289, were investigated, since their properties were reported to be different from many of these described here for ribosephosphate isomerases A and B. In our hands strain X289 contained two ribosephosphate isomerases apparently identical to ribosephosphate isomerases A and B. The evidence to date suggests that ribosephosphate isomerase A catalyses the formation of ribose 5-phosphate from ribulose 5-phosphate and also participates in the reverse reaction during ribose and adenosine catabolism. The normal physiological role of the inducible ribosephosphate isomerase B is still uncertain. << Less

  Eur. J. Biochem. 55:323-332(1975) [PubMed] [EuropePMC]

• The enzymatic conversion of 6-phosphogluconate to ribulose-5-phosphate and ribose-5-phosphate.

  HORECKER B.L., SMYRNIOTIS P.Z., SEEGMILLER J.E.

  J Biol Chem 193:383-396(1951) [PubMed] [EuropePMC]