Self-Association and Allosteric Properties of Glutamine-dependent Carbamyl Phosphate Synthetase

Trotta, Paul P.; Estis, Leonard F.; Meister, Alton; Haschemeyer, Rudy H.

doi:10.1016/s0021-9258(19)43055-x

Cited by 58 publications

(19 citation statements)

References 12 publications

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“…We have used excess Mg2+ and the allosteric activator lornithine in our experiments because the double-reciprocal plot for ATP under these conditions is linear; this is an essential requirement for obtaining a meaningful kinetic scheme for an enzyme with so many substrates and products (Raushel et al, 1978b). The Michaelis constant for ATP is lowered by Lornithine, and this allosteric effector also promotes oligomerization of the enzyme (Trotta et al, 1974). Another difference between the experimental conditions of Powers and Meister and ourselves is that they used up to 14 mM ATP while in our experiments 2.0 mM ATP was the highest concentration used.…”

Section: Discussionmentioning

confidence: 99%

Determination of rate-limiting steps of Escherichia coli carbamoyl-phosphate synthase. Rapid quench and isotope partitioning experiments

Raushel¹,

Villafranca²

1979

Biochemistry

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Section: Discussionmentioning

confidence: 99%

Determination of rate-limiting steps of Escherichia coli carbamoyl-phosphate synthase. Rapid quench and isotope partitioning experiments

Raushel¹,

Villafranca²

1979

Biochemistry

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“…Ornithine and UMP act by decreasing or increasing, respectively, the concentration of MgATP required for halfmaximal velocity. Studies in our laboratory and by Meister and colleagues (Anderson & Marvin, 1970;Trotta et al, 1974;Powers et al, 1980) have shown that the enzyme is subject to self-association, which is differently affected by the presence of allosteric effectors, MgATP, and K+ and is dependent upon enzyme concentration. Positive allosteric effectors, P¡, MgA-TP, and K+ facilitate association.…”

mentioning

confidence: 90%

Carbamoyl-phosphate synthetase: an example of effects on enzyme properties of shifting an equilibrium between active monomer and active oligomer

Anderson¹

1986

Biochemistry

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Carbamoyl-phosphate synthetase from Escherichia coli is subject to allosteric activation by ornithine, allosteric inhibition by uridine 5'-phosphate (UMP), and reversible concentration-dependent self-association. Positive allosteric effectors, magnesium adenosine 5'-triphosphate (MgATP), K+, and inorganic phosphate facilitate association. The purpose of this study was to determine the state of association of carbamoyl-phosphate synthetase in the presence and absence of different substrates and effectors and to consider the basis for the observed effects of enzyme concentration on specific activity. Studies employing gel filtration chromatography have shown that when the concentration of carbamoyl-phosphate synthetase is low (less than 0.01 mg/mL), the enzyme exists as monomer under all conditions, including the presence of UMP in phosphate buffer and the presence of all substrates plus ornithine (conditions that support maximal catalytic activity). At higher enzyme concentrations (e.g., greater than 0.01 mg/mL) the specific activity increases with increasing enzyme concentration when MgATP is nonsaturating but is independent of enzyme concentration when MgATP is saturating or when ornithine is present with MgATP being either saturating or nonsaturating. These results indicate that the catalytic activity of this enzyme is not directly linked to oligomer formation. The theoretical properties and possible significance of a generalized model of enzyme association-dissociation in which the active monomeric form, in equilibrium with another monomeric form, is specifically subject to self-association but the different states of association have the same specific activity, are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Carbamoyl phosphate synthetase (CPS) from Escherichia coli is an extraordinary complex enzyme . Prior experimental evidence has clearly indicated that CPS has three distinct active sites, which collectively convert five separate substrates into five reaction products as shown below: Ammonia can replace glutamine as the ultimate source for the nitrogen requirement in the reaction presented above . A chemical mechanism for the enzymatic transformation is presented below in Scheme .…”

mentioning

confidence: 99%

“…1 Prior experimental evidence has clearly indicated that CPS has three distinct active sites, 2 which collectively convert five separate substrates into five reaction products as shown below: Ammonia can replace glutamine as the ultimate source for the nitrogen requirement in the reaction presented above. 3 A chemical mechanism for the enzymatic transformation is presented below in Scheme 1. The first ATP phosphorylates bicarbonate to form the unstable intermediate, carboxyphosphate.…”

mentioning

confidence: 99%

Channeling of Ammonia through the Intermolecular Tunnel Contained within Carbamoyl Phosphate Synthetase

Mullins

Raushel

1999

J. Am. Chem. Soc.

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Self-Association and Allosteric Properties of Glutamine-dependent Carbamyl Phosphate Synthetase

Cited by 58 publications

References 12 publications

Determination of rate-limiting steps of Escherichia coli carbamoyl-phosphate synthase. Rapid quench and isotope partitioning experiments

Determination of rate-limiting steps of Escherichia coli carbamoyl-phosphate synthase. Rapid quench and isotope partitioning experiments

Carbamoyl-phosphate synthetase: an example of effects on enzyme properties of shifting an equilibrium between active monomer and active oligomer

Channeling of Ammonia through the Intermolecular Tunnel Contained within Carbamoyl Phosphate Synthetase

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