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Related Concept Videos

Catalytically Perfect Enzymes01:07

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.
Protein Complexes with Interchangeable Parts01:57

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
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...
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...
Enzymes02:34

Enzymes

Inside living organisms, enzymes act as catalysts for many biochemical reactions involved in cellular metabolism. The role of enzymes is to reduce the activation energies of biochemical reactions by forming complexes with its substrates. The lowering of activation energies favor an increase in the rates of biochemical reactions.
Enzyme deficiencies can often translate into life-threatening diseases. For example, a genetic abnormality resulting in the deficiency of the enzyme G6PD...
Induced-fit Model01:13

Induced-fit Model

Most chemical reactions in cells require enzymes—biological catalysts that speed up the reaction without being consumed or permanently changed. They reduce the activation energy needed to convert the reactants into products. Enzymes are proteins, that usually work by binding to a substrate—a reactant molecule that they act upon.
Enzymes exhibit substrate specificity, meaning that they can only bind to certain substrates. This is mainly determined by the shape and chemical characteristics of...

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High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli
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High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli

Published on: August 13, 2011

Product binding varies dramatically between processive and nonprocessive cellulase enzymes.

Lintao Bu1, Mark R Nimlos, Michael R Shirts

  • 1National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA. lintao.bu@nrel.gov

The Journal of Biological Chemistry
|June 1, 2012
PubMed
Summary
This summary is machine-generated.

Cellulases, enzymes that break down cellulose, show significant product inhibition differences. Processive cellulases bind products more strongly than nonprocessive ones, impacting their efficiency.

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Expression of Recombinant Cellulase Cel5A from Trichoderma reesei in Tobacco Plants
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Last Updated: May 21, 2026

High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli
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Published on: August 13, 2011

High-throughput Screening of Carbohydrate-degrading Enzymes Using Novel Insoluble Chromogenic Substrate Assay Kits
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Expression of Recombinant Cellulase Cel5A from Trichoderma reesei in Tobacco Plants
13:05

Expression of Recombinant Cellulase Cel5A from Trichoderma reesei in Tobacco Plants

Published on: June 13, 2014

Area of Science:

  • Biochemistry
  • Enzymology
  • Structural Biology

Background:

  • Cellulases are crucial enzymes that hydrolyze β-1,4 glycosidic linkages in cellulose, a highly abundant biopolymer.
  • Product inhibition is a known factor affecting cellulase efficiency, but experimental data on product-binding affinities are inconsistent.
  • Understanding product inhibition is key to optimizing cellulase applications in biotechnology and biofuel production.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying product inhibition in cellulases.
  • To compare the binding affinities of cellobiose to processive and nonprocessive cellulases.
  • To elucidate the role of enzyme structure, specifically tunnel versus cleft active sites, in product binding.

Main Methods:

  • Calculation of binding free energy for cellobiose to the product sites of glycoside hydrolase families 6 and 7 cellulases.
  • Comparative analysis of processive and nonprocessive cellulase structures, focusing on active site architecture and ligand interactions.
  • In silico prediction of the effect of a bound cellodextrin on product binding affinity.

Main Results:

  • Cellobiose binds significantly more strongly to processive cellulases than to nonprocessive cellulases.
  • Product binding to processive cellulases is enhanced by the presence of a cellodextrin in the reactant site, while nonprocessive cellulases are unaffected.
  • Structural features, including longer tunnel-forming loops and specific hydrogen bonding in processive cellulases, stabilize product binding.

Conclusions:

  • The study reveals distinct mechanisms of product inhibition between processive and nonprocessive cellulases, driven by structural differences in their active sites.
  • Product inhibition is predicted to be more significant for processive cellulases, especially under conditions favoring productive substrate binding.
  • These findings help reconcile discrepancies in experimental binding data and provide a molecular basis for enzyme engineering efforts.