Uridine-5′-phosphate synthase: Evidence for substrate cycling involving this bifunctional protein

Traut, Thomas W.

doi:10.1016/0003-9861(89)90570-5

Cited by 7 publications

(3 citation statements)

References 20 publications

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“…In addition to the present studies demonstrating that stability is a benefit of the bifunctional architecture, the extent to which OMP channeling may occur remains to be explored. While our earlier studies with cell extracts showed that channeling of OMP was incomplete (8), with the availability of pure UMP synthase and the two domains, future studies will compare the efficiency of OMP transfer within the bifunctional enzyme in comparison to a mixture of the two domains.…”

Section: Fig 2 Stability Of the Dilute Human Odcase Catalytic Centermentioning

confidence: 99%

“…Channeling of intermediate metabolites between catalytic centers remains a controversial topic as shown in a recent symposium (7), with channeling being supported with some enzymes but not for others. Our earlier studies had tested the channeling hypothesis for UMP synthase with mouse cell extracts, which would contain normal quantities of enzymes that might compete for any OMP being formed by the OPRTase domain of UMP synthase (8). These studies showed that channeling was not efficient, since part of the OMP made by UMP synthase was readily converted to orotidine by an available phosphatase activity, thereby verifying that some OMP had to have diffused into the bulk solvent during the assay.…”

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confidence: 99%

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Intrinsic Activity and Stability of Bifunctional Human UMP Synthase and Its Two Separate Catalytic Domains, Orotate Phosphoribosyltransferase and Orotidine-5′-phosphate Decarboxylase

Yablonski

Pasek

Han

et al. 1996

Journal of Biological Chemistry

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Human UMP synthase is a bifunctional protein containing two separate catalytic domains, orotate phosphoribosyltransferase (EC 2.4.2.10) and orotidine-5'-phosphate decarboxylase (EC 4.1.1.23). These studies address the question of why the last two reactions in pyrimidine nucleotide synthesis are catalyzed by a bifunctional enzyme in mammalian cells, but by two separate enzymes in microorganisms. From existing data on subunit associations of the respective enzymes and calculations showing the molar concentration of enzyme to be far lower in mammalian cells than in microorganisms, we hypothesize that the covalent union in UMP synthase stabilizes the domains containing the respective catalytic centers. Evidence supporting this hypothesis comes from studies of stability of enzyme activity in vitro, at physiological concentrations, of UMP synthase, the two isolated catalytic domains prepared by site-directed mutagenesis of UMP synthase, and the yeast ODCase. The two engineered domains have activities very similar to the native UMP synthase, but unlike the bifunctional protein, the domains are quite unstable under conditions promoting the dissociated monomer.

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Section: Fig 2 Stability Of the Dilute Human Odcase Catalytic Centermentioning

confidence: 99%

mentioning

confidence: 99%

Intrinsic Activity and Stability of Bifunctional Human UMP Synthase and Its Two Separate Catalytic Domains, Orotate Phosphoribosyltransferase and Orotidine-5′-phosphate Decarboxylase

Yablonski

Pasek

Han

et al. 1996

Journal of Biological Chemistry

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“…Although the two domains of UMP synthase catalyze sequential metabolic steps, evidence for the strict channeling of the common metabolite (OMP) between the two domains was not observed (26). However, with the ability to separately clone and express the two domains for the human UMP synthase, it was shown that the bifunctional protein has much greater stability than either of the independent catalytic domains (27), and such a benefit may explain two different gene fusion events to produce UMP synthase.…”

Section: Emericella Nidulans Endomyces Magnusii Epichloe Typhinamentioning

confidence: 99%

The Chemistry of the Reaction Determines the Invariant Amino Acids during the Evolution and Divergence of Orotidine 5′-Monophosphate Decarboxylase

Traut

Temple

2000

Journal of Biological Chemistry

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Orotidine 5-phosphate (OMP) decarboxylase has the largest rate enhancement for any known enzyme. For an average protein of 270 amino acids from more than 80 species, only 8 amino acids are invariant, and 7 of these correspond to ligand-binding residues in the crystal structures of the enzyme from four species. It appears that the chemistry required for catalysis determines the invariant residues for this enzyme structure. A motif of three invariant amino acids at the catalytic site (DXKXXD) is also found in the enzyme hexulose-phosphate synthase. Although the core of OMP decarboxylase is conserved, it has undergone a variety of changes in subunit size or fusion to other protein domains, such as orotate phosphoribosyltransferase, during evolution in different kingdoms. The phylogeny of OMP decarboxylase shows a unique subgroup distinct from the three kingdoms of life. The enzyme subunit size almost doubles from Archaea (average mass of 24.5 kDa) to certain fungi (average mass of 41.7 kDa). These observed changes in subunit size are produced by insertions at 12 sites, largely in loops and on the exterior of the core protein. The consensus for all sequences has a minimal size of <20 kDa.

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Principles of Regulation and Control in Biochemistry: A Pragmatic, Flux‐Oriented Approach

Crabtree¹,

Newsholme

Reppas

1997

Comprehensive Physiology

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The sections in this article are: Flux‐Oriented Theory of Regulation Flux‐Generating Steps Branched Fluxes: Reversible Reactions Other Types of Flux: Energy Fluxes and Equivalence Internal and External Effectors Control and Regulation of Metabolic Fluxes and Concentrations: Communication and Regulatory Sequences Control Versus Regulation Identification of Communication Sequences In Vivo Need for Sensitive Regulation In Vivo Metabolic Sensitivities Analysis of Non‐Steady States Two Other Important Approaches to Metabolic Control and Regulation Biochemical Systems Theory ( BST ) Metabolic Control Theory ( MCT ) Summary and Future Prospects

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Uridine-5′-phosphate synthase: Evidence for substrate cycling involving this bifunctional protein

Cited by 7 publications

References 20 publications

Intrinsic Activity and Stability of Bifunctional Human UMP Synthase and Its Two Separate Catalytic Domains, Orotate Phosphoribosyltransferase and Orotidine-5′-phosphate Decarboxylase

Intrinsic Activity and Stability of Bifunctional Human UMP Synthase and Its Two Separate Catalytic Domains, Orotate Phosphoribosyltransferase and Orotidine-5′-phosphate Decarboxylase

The Chemistry of the Reaction Determines the Invariant Amino Acids during the Evolution and Divergence of Orotidine 5′-Monophosphate Decarboxylase

Principles of Regulation and Control in Biochemistry: A Pragmatic, Flux‐Oriented Approach

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