A highly reactive beta-galactosidase (Escherichia coli) resulting from a substitution of an aspartic acid for Gly-794.

Martínez‐Bilbao, Mercedes; Holdsworth, R E; Edwards, L. A.; Huber, R.E.

doi:10.1016/s0021-9258(19)67745-8

Cited by 38 publications

(8 citation statements)

References 37 publications

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“…This estimate is an order of magnitude greater than the value 3.6 × 10 3 min −1 given in Ref. [22], but the two estimates agree closely when one considers that β-gal converts about half of its lactose substrate to glucose and galactose, rather than allolactose, and that the enzyme is composed of four monomeric catalytic subunits. The estimate given in Ref.…”

Section: Parameter Valuessupporting

confidence: 47%

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Determinants of bistability in induction of the Escherichia coli lac operon

et al. 2008

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We have developed a mathematical model of regulation of expression of the Escherichia coli lac operon, and have investigated bistability in its steady-state induction behavior in the absence of external glucose.Numerical analysis of equations describing regulation by artificial inducers revealed two natural bistability parameters that can be used to control the range of inducer concentrations over which the model exhibits bistability. By tuning these bistability parameters, we found a family of biophysically reasonable systems that are consistent with an experimentally determined bistable region for induction by thio-methylgalactoside (Ozbudak et al. Nature 427:737, 2004). The model predicts that bistability can be abolished when passive transport or permease export becomes sufficiently large; the former case is especially relevant to induction by isopropyl-β, D-thiogalactopyranoside. To model regulation by lactose, we developed similar equations in which allolactose, a metabolic intermediate in lactose metabolism and a natural inducer of lac, is the inducer. For biophysically reasonable parameter values, these equations yield no bistability in response to induction by lactose; however, systems with an unphysically small permease-dependent export effect can exhibit small amounts of bistability for limited ranges of parameter values. These results cast doubt on the relevance of bistability in the lac operon within the natural context of E. coli, and help shed light on the controversy among existing theoretical studies that address this issue. The results also suggest an experimental approach to address the relevance of bistability in the lac operon within the natural context of E. coli.

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Section: Parameter Valuessupporting

confidence: 47%

“…The estimate given in Ref. [22] is appropriate for total turnover of lactose on a per monomer basis. Like for α, because measurements were performed at 30 • C, we consider a range of values ten times lower to ten times higher than the nominal value.…”

Section: Parameter Valuesmentioning

confidence: 99%

Determinants of bistability in induction of the Escherichia coli lac operon

et al. 2008

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“…We estimate these parameters from the data reported in Martínez-Bilbao et al (1991) as f L 2 3:60 3 10 3 min ÿ1 ;…”

Section: Lactose and Allolactose Dynamics Parametersmentioning

confidence: 99%

Influence of Catabolite Repression and Inducer Exclusion on the Bistable Behavior of the lac Operon

Santillán

Mackey

2004

Biophysical Journal

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A mathematical model of the lac operon which includes all of the known regulatory mechanisms, including external-glucose-dependent catabolite repression and inducer exclusion, as well as the time delays inherent to transcription and translation, is presented. With this model we investigate the influence of external glucose, by means of catabolite repression and the regulation of lactose uptake, on the bistable behavior of this system.

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“…With E. coli β-Gal and ONPG, k 2 ≫ k 3 , meaning that the second is the rate-limiting step of the reaction. , Up to our knowledge, the rate constant values for the K. lactis β-Gal-catalyzed hydrolysis of ONPG are not available, but we can compare the k 2 and k 3 for the lactose hydrolysis catalyzed by E.…”

Section: Discussionmentioning

confidence: 99%

“…lactis β-Gal-catalyzed hydrolysis of ONPG are not available, but we can compare the k 2 and k 3 for the lactose hydrolysis catalyzed by E. coli β-Gal (60 and 1200 s –1 , respectively) and by K. lactis β-Gal (1.58 and 4.49 s –1 , respectively) .…”

Section: Discussionmentioning

confidence: 99%

Effect of Polyethylene Glycol-Induced Molecular Crowding on the Enzymatic Activity and Thermal Stability of β-Galactosidase from Kluyveromyces lactis

Nolan

Collin

Rodríguez

et al. 2020

J. Agric. Food Chem.

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Here, we report the effect of polyethylene glycol (PEG 6000 )-induced molecular crowding (MC) on the catalytic activity and thermal stability of Kluyveromyces lactis β-galactosidase (β-Gal). The β-Gal-catalyzed hydrolysis of o-nitrophenyl-β-Dgalactopyranoside followed a Michaelian kinetics at [PEG 6000 ] ≤ 25% w/v and positive cooperativity at higher concentrations (35% w/v PEG 6000 ). Compared with dilute solutions, in the MC media, β-Gal exhibited stronger thermal stability, as shown by the increase in the residual activity recovered after preincubation at high temperatures (e.g., 45 °C) and by the slower inactivation kinetics. Considering the effects of water thermodynamic activity on the reaction kinetics and protein structure and the effect of the exclusion volume on protein conformation, we suggest that changes in the protein oligomerization state and hydration could be the responsible for the behavior observed at the highest MC levels assayed. These results could be relevant and should be taken into account in industrial food processes applying β-Gal from K. lactis.

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A highly reactive beta-galactosidase (Escherichia coli) resulting from a substitution of an aspartic acid for Gly-794.

Cited by 38 publications

References 37 publications

Determinants of bistability in induction of the Escherichia coli lac operon

Determinants of bistability in induction of the Escherichia coli lac operon

Influence of Catabolite Repression and Inducer Exclusion on the Bistable Behavior of the lac Operon

Effect of Polyethylene Glycol-Induced Molecular Crowding on the Enzymatic Activity and Thermal Stability of β-Galactosidase from Kluyveromyces lactis

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