Enzyme

Ribbon diagram of glycosidase with an arrow showing the cleavage of the maltose sugar substrate into two glucose products.
The enzyme glucosidase converts the sugar maltose into two glucose sugars. Active site residues in red, maltose substrate in black, and NAD cofactor in yellow. (PDB: 1OBB​)

Enzymes (/ˈɛnzmz/) are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life.[1]: 8.1  Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called enzymology and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties.[2][3]

Enzymes are known to catalyze more than 5,000 biochemical reaction types.[4]

Other biocatalysts are catalytic RNA molecules, also called ribozymes. They are sometimes described as a type of enzyme rather than being like an enzyme, but even in the decades since ribozymes' discovery in 1980–1982, the word enzyme alone often means the protein type specifically (as is used in this article).

An enzyme's specificity comes from its unique three-dimensional structure.

IUPAC definition for enzymes

Like all catalysts, enzymes increase the reaction rate by lowering its activation energy. Some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5'-phosphate decarboxylase, which allows a reaction that would otherwise take millions of years to occur in milliseconds.[5][6] Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. Enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Many therapeutic drugs and poisons are enzyme inhibitors. An enzyme's activity decreases markedly outside its optimal temperature and pH, and many enzymes are (permanently) denatured when exposed to excessive heat, losing their structure and catalytic properties.

Some enzymes are used commercially, for example, in the synthesis of antibiotics. Some household products use enzymes to speed up chemical reactions: enzymes in biological washing powders break down protein, starch or fat stains on clothes, and enzymes in meat tenderizer break down proteins into smaller molecules, making the meat easier to chew.

  1. ^ Stryer L, Berg JM, Tymoczko JL (2002). Biochemistry (5th ed.). San Francisco: W.H. Freeman. ISBN 0-7167-4955-6.Open access icon
  2. ^ Murphy JM, Farhan H, Eyers PA (April 2017). "Bio-Zombie: the rise of pseudoenzymes in biology". Biochemical Society Transactions. 45 (2): 537–544. doi:10.1042/bst20160400. PMID 28408493.
  3. ^ Murphy JM, Zhang Q, Young SN, Reese ML, Bailey FP, Eyers PA, et al. (January 2014). "A robust methodology to subclassify pseudokinases based on their nucleotide-binding properties". The Biochemical Journal. 457 (2): 323–334. doi:10.1042/BJ20131174. PMC 5679212. PMID 24107129.
  4. ^ Schomburg I, Chang A, Placzek S, Söhngen C, Rother M, Lang M, et al. (January 2013). "BRENDA in 2013: integrated reactions, kinetic data, enzyme function data, improved disease classification: new options and contents in BRENDA". Nucleic Acids Research. 41 (Database issue): D764–D772. doi:10.1093/nar/gks1049. PMC 3531171. PMID 23203881.
  5. ^ Radzicka A, Wolfenden R (January 1995). "A proficient enzyme". Science. 267 (5194): 90–93. Bibcode:1995Sci...267...90R. doi:10.1126/science.7809611. PMID 7809611. S2CID 8145198.
  6. ^ Callahan BP, Miller BG (December 2007). "OMP decarboxylase--An enigma persists". Bioorganic Chemistry. 35 (6): 465–469. doi:10.1016/j.bioorg.2007.07.004. PMID 17889251.

From Wikipedia, the free encyclopedia · View on Wikipedia

Developed by Nelliwinne