Bacillus cereus Phosphopentomutase Is an Alkaline Phosphatase Family Member That Exhibits an Altered Entry Point into the Catalytic Cycle

Journal Article · Thu Sep 15 00:00:00 EDT 2011 · J. Biol. Chem.

DOI:https://doi.org/10.1074/jbc.M110.201350· OSTI ID:1021786

Panosian, Timothy D; Nannemann, David P; Watkins, Guy R; Phelan, Vanessa V; McDonald, W Hayes; Wadzinski, Brian E; Bachmann, Brian O; Iverson, Tina M ^[1]

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1. Vanderbilt

Bacterial phosphopentomutases (PPMs) are alkaline phosphatase superfamily members that interconvert {alpha}-D-ribose 5-phosphate (ribose 5-phosphate) and {alpha}-D-ribose 1-phosphate (ribose 1-phosphate). We investigated the reaction mechanism of Bacillus cereus PPM using a combination of structural and biochemical studies. Four high resolution crystal structures of B. cereus PPM revealed the active site architecture, identified binding sites for the substrate ribose 5-phosphate and the activator {alpha}-D-glucose 1,6-bisphosphate (glucose 1,6-bisphosphate), and demonstrated that glucose 1,6-bisphosphate increased phosphorylation of the active site residue Thr-85. The phosphorylation of Thr-85 was confirmed by Western and mass spectroscopic analyses. Biochemical assays identified Mn{sup 2+}-dependent enzyme turnover and demonstrated that glucose 1,6-bisphosphate treatment increases enzyme activity. These results suggest that protein phosphorylation activates the enzyme, which supports an intermolecular transferase mechanism. We confirmed intermolecular phosphoryl transfer using an isotope relay assay in which PPM reactions containing mixtures of ribose 5-[{sup 18}O{sub 3}]phosphate and [U-{sup 13}C{sub 5}]ribose 5-phosphate were analyzed by mass spectrometry. This intermolecular phosphoryl transfer is seemingly counter to what is anticipated from phosphomutases employing a general alkaline phosphatase reaction mechanism, which are reported to catalyze intramolecular phosphoryl transfer. However, the two mechanisms may be reconciled if substrate encounters the enzyme at a different point in the catalytic cycle.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: UNIVERSITYNIH
• OSTI ID: 1021786
• Journal Information: J. Biol. Chem., Vol. 286, Issue (10) ; 03, 2011; ISSN 0021-9258
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ALKALINE PHOSPHATASE
BACILLUS CEREUS
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
ENZYME ACTIVITY
ENZYMES
GLUCOSE
MASS SPECTROSCOPY
METABOLISM
MIXTURES
PHOSPHATASES
PHOSPHORYLATION
PROTEINS
REACTION KINETICS
RESIDUES
RESOLUTION
RIBOSE
SUBSTRATES
TRANSFERASES