Enzymes I​: Catalysis, Chemical catalyst, Biocatalyst, Deference between chemical catalyst and Biocatalyst, Brief history of enzymes, Properties of enzymes, Composition of enzymes, Cofactors and coenzymes, Active sites,  Classification of enzymes​

Enzymes I​: Catalysis, Chemical catalyst, Biocatalyst, Deference between chemical catalyst and Biocatalyst, Brief history of enzymes, Properties of enzymes, Composition of enzymes, Cofactors and coenzymes, Active sites, Classification of enzymes​

February 20, 2022

Enzyme I: Catalysis, Chemical catalyst, Biocatalyst, Deference between chemical catalyst and Biocatalyst, Brief history of enzymes, Properties of enzymes, Composition of enzymes, Cofactors and coenzymes, Active sites,  Classification of enzymes

  • Catalysis is the change in rate of a chemical/Biochemical reaction due to the change in activation energy of that reaction by the involvement of a catalyst. 
  • Catalysts are the Substance that increase or decrease the rate of a chemical reaction but remain unchanged
  • A catalyst generally brings down the energy of the activated state and thus the catalytic reactions have a lower rate-limiting free energy of activation than the corresponding unanalyzed reaction, resulting in higher reaction rate at the same temperature
  • Biocatalyst a.k.a. Enzymes are proteins that increase rate of biochemical reactions converting substrate into product.

Properties of enzymes

  • As almost all Enzymes are proteins, their ability to catalyze reactions is attributable to their primary, secondary, tertiary, and quaternary structures
  • Enzymes accelerate chemical reactions tremendously
  • Highly specific with respect to their reactants
  • Work at specific temperature, pH and substrate concentration
  • Get denature at high temperature and extremes pH
  • Generally do not change during the course of reaction
  •  Catalyze only thermodynamically possible reactions 
  • A small amount of enzyme is sufficient for a large change in the rate of reaction
  •  Don’t change the position of equilibrium and direction of the reaction
  •  Enhance rate of any chemical reaction by decreasing the activation energy barrier of reactants
  • Usually act by forming a transient complex with the reactant, thus stabilizing the transition state
  • Reactants of enzyme catalyzed reaction are called substrates

History

  • 1833: Enzyme was isolated from aqueous extract of malt when ethanol was added. The heat-labile precipitate is now known as amylase was utilized to hydrolyze starch to soluble sugar.
  • 1878:  Enzymes term was coined by Kuhne to explain the substances present in the yeast that can convert sugar in to alcohol
  • 1890: Emil Fischer suggested key/lock mechanism of enzyme action
  • 1897: Eduard and Hans Buchner showed dead yeast cell extracts can perform reactions of living cells that is conversion of sugar in to CO2 and alcohol. 
  • 1928: J B Sumner succeeded in crystallization of enzyme urease for the first time and stated the proteinaceous nature of enzyme. Later, in 1946, Sumner  received the Nobel Prize for his work with the enzyme urease.
  • 1930- Northrop and Stanley purified digestive enzymes pepsin, trypsin and chymotrypsin.

Composition of Enzymes​

  • Simple Enzymes: Some enzymes are made of only polypeptide chain and do not require any additional chemical groups or molecule for their activities are called simple enzyme. 
  • Holoenzymes: Some enzymes require an additional chemical component for their activities called a cofactor—either one or more inorganic ions, such as Fe+2, Mg+2, Mn+2, or Zn+2 or a complex organic or metalloorganic molecule called a coenzyme. 
  • Coenzymes act as transient carriers of specific functional groups). Most are derived from vitamins, organic nutrients required in small amounts in the diet. 
  • Some enzymes require both a coenzyme and one or more metal ions for activity
  • A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein is called a prosthetic group. 
  • A complete, catalytically active enzyme together with its bound coenzyme and/or metal ions is called a holoenzyme
  • The protein part of an enzyme is called the apoenzyme or apoprotein.  

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