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Related Concept Videos

Cofactors and Coenzymes01:24

Cofactors and Coenzymes

Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic interactions or acid-base reactions. However, amino acids cannot catalyze oxidation-reduction and group transfer reactions and need to be aided by non-protein components called cofactors. Cofactors are also referred to as the chemical teeth of an enzyme.
Cofactors can be metallic ions or organic molecules called coenzymes. These types of helper...
Cofactors and Coenzymes01:27

Cofactors and Coenzymes

Enzymes require additional components for proper function. There are two such classes of molecules: cofactors and coenzymes. Cofactors are metallic ions and coenzymes are non-protein organic molecules. Both of these types of helper molecule can be tightly bound to the enzyme or bound only when the substrate binds.
Cofactors and Coenzymes01:27

Cofactors and Coenzymes

Enzymes require additional components for proper function. There are two such classes of molecules: cofactors and coenzymes. Cofactors are metallic ions and coenzymes are non-protein organic molecules. Both of these types of helper molecule can be tightly bound to the enzyme or bound only when the substrate binds.
Introduction to Mechanisms of Enzyme Catalysis01:13

Introduction to Mechanisms of Enzyme Catalysis

For many years, scientists thought that enzyme-substrate binding took place in a simple "lock-and-key" fashion. This model stated that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild...
Introduction to Mechanisms of Enzyme Catalysis01:13

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For many years, scientists thought that enzyme-substrate binding took place in a simple "lock-and-key" fashion. This model stated that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild...
Introduction to Enzymes01:22

Introduction to Enzymes

The use of enzymes by humans dates to 7000 BCE. Humans first used enzymes to ferment sugars and produce alcohol without knowing that this was an enzyme-catalyzed reaction. Wilhelm Kuhne coined the term 'enzyme' in 1877 from the Greek words ‘en’ meaning ‘in’ or ‘within’ and ‘zyme’ meaning ‘yeast.’
Most enzymes are proteins that speed up biochemical reactions without being consumed. Enzymes contain one or more active sites that bind the substrates and convert them into products. Many enzymes also...

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How does an enzyme recognize CO2?

Julien J H Cotelesage1, Jennifer Puttick, Hughes Goldie

  • 1Department of Biochemistry, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Sask., Canada.

The International Journal of Biochemistry & Cell Biology
|May 4, 2007
PubMed
Summary

Phosphoenolpyruvate carboxykinase (PCK) uses carbon dioxide, not bicarbonate, for carboxylation. Structural and kinetic data reveal how PCK binds CO(2), highlighting the role of basic amino acid residues in catalysis.

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Area of Science:

  • Biochemistry
  • Enzymology
  • Structural Biology

Background:

  • Phosphoenolpyruvate carboxykinase (PCK) catalyzes a key reversible carboxylation reaction.
  • The precise substrate (CO(2) vs. bicarbonate) and binding mechanism of PCK have been areas of investigation.

Purpose of the Study:

  • To elucidate the substrate specificity of PCK, specifically whether it utilizes carbon dioxide or bicarbonate.
  • To determine the structural basis for CO(2) binding and activation by PCK.
  • To investigate the role of specific amino acid residues in the catalytic mechanism.

Main Methods:

  • Enzyme kinetics assays comparing CO(2) and bicarbonate as substrates.
  • X-ray crystallography to determine the structures of Escherichia coli PCK in complex with CO(2).
  • Site-directed mutagenesis to probe the function of key amino acid residues.

Main Results:

  • PCK exhibits significantly higher activity with CO(2) compared to bicarbonate.
  • Two crystal structures reveal the binding site and orientation of CO(2) within the PCK active site, influenced by a manganese ion.
  • Comparison with other protein-CO(2) complexes shows a conserved interaction involving hydrogen bonding between CO(2) and basic amino acid residues.
  • A mutant PCK (Arg65Gln) showed altered substrate kinetics but maintained CO(2) binding affinity, suggesting a conserved hydrogen bond.

Conclusions:

  • PCK preferentially utilizes carbon dioxide as its substrate for carboxylation.
  • The crystal structures provide insights into the mechanism of CO(2) binding and polarization, facilitated by basic residues like Arg65.
  • The findings contribute to understanding the broader mechanisms of carbon fixation in biological systems.