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Related Concept Videos

Enzyme Kinetics01:19

Enzyme Kinetics

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Enzymes speed up reactions by lowering the activation energy of the reactants. The speed at which the enzyme turns reactants into products is called the rate of reaction. Several factors impact the rate of reaction, including the number of available reactants. Enzyme kinetics is the study of how an enzyme changes the rate of a reaction.
Scientists typically study enzyme kinetics with a fixed amount of enzyme in the controlled environment of a test tube. When more reactant, or substrate, is...
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Enzymes02:34

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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.
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Enzyme kinetics studies the rates of biochemical reactions. Scientists monitor the reaction rates for a particular enzymatic reaction at various substrate concentrations. Additional trials with inhibitors or other molecules that affect the reaction rate may also be performed.
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Introduction to Enzymes01:22

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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.’
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Multi-enzyme Screening Using a High-throughput Genetic Enzyme Screening System
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Profiling the orphan enzymes.

Maria Sorokina1, Mark Stam, Claudine Médigue

  • 1Direction des Sciences du Vivant, Commissariat à l'Energie Atomique (CEA), Institut de Génomique, Genoscope, Laboratoire d'Analyses Bioinformatiques pour la Génomique et le Métabolisme, 2 rue Gaston Crémieux, 91057 Evry, France. msorokina@genoscope.cns.fr.

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|June 8, 2014
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Summary
This summary is machine-generated.

Next Generation Sequencing data offers enzyme discovery potential, yet many enzyme activities remain "orphan enzymes" lacking protein sequences. This review updates orphan enzyme surveys, finding a decrease but still significant numbers, especially in metabolic databases.

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Area of Science:

  • Biochemistry
  • Bioinformatics
  • Enzymology

Background:

  • Next Generation Sequencing generates vast data, increasing potential for novel enzyme discovery.
  • A significant number of known enzyme activities lack associated protein sequences, termed "orphan enzymes".

Purpose of the Study:

  • To provide an updated survey of orphan enzymes by analyzing public databases.
  • To investigate "local orphan enzymes" and assess the potential for their identification through homology searches.
  • To explore the relationship between protein domains and enzyme activities to address the orphan enzyme problem.

Main Methods:

  • Mining public databases for orphan enzyme data.
  • Analyzing Enzyme Commission (EC) classification and metabolic databases.
  • Utilizing the PRIAM software for homology-based candidate protein identification.
  • Studying the association between protein domains and catalyzed activities.

Main Results:

  • The percentage of orphan enzyme activities decreased from 38% to 22% over ten years.
  • Over 1,000 orphan enzymes exist within the 5,000 EC entries; nearly 50% of metabolic reactions are orphans.
  • More than 30% of EC activities show incomplete sequence information across superkingdoms, with bias in Archaea.
  • Homology searches using PRIAM can identify candidate proteins for a substantial fraction of local orphan enzymes.
  • Newly discovered enzymes are frequently linked to known enzyme domains.

Conclusions:

  • Despite progress, a considerable number of orphan enzymes persist, particularly within metabolic pathways.
  • Exploiting enzyme promiscuity and multifunctionality within known families offers a strategy to identify orphan enzymes.
  • Recent initiatives focus on finding proteins for orphan enzymes and discovering novel enzymatic activities.