Enzyme substrate

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate(s). The substrate binds with the enzyme's active site, and an enzyme-substrate complex is formed. The substrate is broken down into a product and is released from the active site. The active site is now free to accept another substrate molecule. For example, in the reaction that occurs upon adding the enzyme rennin in milk, causing milk's coagulation, the substrate is milk and the enzyme is rennin. Another example is the reaction of the enzyme catalase in the decomposition of hydrogen peroxide, in which the enzyme is left the same and the substrate is changed.

:2 H2O2 → 2 H2O + O2.

A general equation is as follows:

: E + S ⇌ ES → EP ⇌ E + P

where E = enzyme, S = substrate(s), P = product(s)Note that only the middle step is irreversible.

By increasing the substrate concentration, the rate of reaction will increase due to the likelihood that the number of enzyme-substrate complexes will increase; this occurs until the enzyme becomes the limiting factor.

Importantly, the substrates that a given enzyme can turn over "in vitro" may not necessarily reflect the physiological, endogenous substrates of the enzyme "in vivo". For example, while fatty acid amide hydrolase (FAAH) can hydrolyze the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide at comparable rates "in vitro", genetic or pharmacological disruption of FAAH elevates anandamide but not 2-AG, suggesting that 2-AG is not an endogenous, "in vivo" substrate for FAAH. [Cravatt BF, Demarest K, Patricelli MP, Bracey MH, Giang DK, Martin BR, Lichtman AH. (2001) Supersensitivity to anandamide and enhanced endogenous cannabinoid signaling in mice lacking fatty acid amide hydrolase. Proc. Natl. Acad. Sci. USA. 98(16):9371-9376.] In another example, the "N"-acyl taurines (NATs) are observed to increase dramatically in FAAH-disrupted animals, but are actually poor "in vitro" FAAH substrates. [Saghatelian A, Trauger SA, Want EJ, Hawkins EG, Siuzdak G, and Cravatt BF. (2004) Assignment of endogenous substrates to enzymes by global metabolite profiling. Biochemistry. 43(45):14332-14339.]

References

ee also

* Enzyme kinetics
* Enzyme assay
* Enzyme catalysis
* Pseudosubstrate


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Enzyme kinetics — is the study of the chemical reactions that are catalysed by enzymes, with a focus on their reaction rates. The study of an enzyme s kinetics reveals the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled,… …   Wikipedia

  • Enzyme inhibitor — Enzyme inhibitors are molecules that bind to enzymes and decrease their activity. Since blocking an enzyme s activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and… …   Wikipedia

  • Enzyme catalysis — is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions. The mechanism of enzyme catalysis is similar …   Wikipedia

  • Substrate analog — Substrate analogs, or transition state analogs, are molecules that can be recognized and bound by an enzyme because they sufficiently resemble that enzyme s substrate. However, the enzyme is unable to affect the analog in the same manner it can… …   Wikipedia

  • Substrate — may mean: *Substrate (aquarium), the material used in the bottom of an aquarium *Substrate (biochemistry), a molecule that is acted upon by an enzyme *Substrate (materials science), the material on which a process is conducted *Substrate… …   Wikipedia

  • Enzyme-linked Immunosorbent Assay — (ELISA) bezeichnet ein antikörperbasiertes Nachweisverfahren (Assay). Wie der Radioimmunassay (RIA) gehört auch der ELISA zur Gruppe der Immunassay Verfahren, basiert aber nicht auf einer Radioaktivitätsmessung, sondern auf einer enzymatischen… …   Deutsch Wikipedia

  • Enzyme — Biocatalyst redirects here. For the use of natural catalysts in organic chemistry, see Biocatalysis. Human glyoxalase I. Two zinc ions that are needed for the enzyme to catalyze its reaction are shown as purp …   Wikipedia

  • Enzyme assay — Beckman DU640 UV/Vis spectrophotometer. Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition. Contents …   Wikipedia

  • Substrate channeling — is when the intermediary metabolic product of one enzyme is passed directly to another enzyme or active site without being released into solution. When several consecutive enzymes of a metabolic pathway channel substrates between themselves, this …   Wikipedia

  • Substrate-level phosphorylation — is a type of chemical reaction that results in the formation of adenosine triphosphate (ATP) by the direct transfer of a phosphate group to adenosine diphosphate (ADP) from a reactive intermediate. In cells, it occurs primarily in the cytoplasm… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.