Enzyme Structure and Function (OpenStax Chemistry 2e)
The study of enzymes is an important interconnection between biology and chemistry. Enzymes are usually proteins (polypeptides) that help to control the rate of chemical reactions between biologically important compounds, particularly those that are involved in cellular metabolism. Different classes of enzymes perform a variety of functions, as shown in Table 1.
Classes of Enzymes and Their Functions
|transferases||transfer of functional groups|
|lyases||group elimination to form double bonds|
|ligases||bond formation with ATP hydrolysis|
Enzyme molecules possess an active site, a part of the molecule with a shape that allows it to bond to a specific substrate (a reactant molecule), forming an enzyme-substrate complex as a reaction intermediate. There are two models that attempt to explain how this active site works. The most simplistic model is referred to as the lock-and-key hypothesis, which suggests that the molecular shapes of the active site and substrate are complementary, fitting together like a key in a lock. The induced fit hypothesis, on the other hand, suggests that the enzyme molecule is flexible and changes shape to accommodate a bond with the substrate. This is not to suggest that an enzyme’s active site is completely malleable, however. Both the lock-and-key model and the induced fit model account for the fact that enzymes can only bind with specific substrates, since in general a particular enzyme only catalyzes a particular reaction (Figure 1).
Flowers, P., Theopold, K., Langley, R., & Robinson, W. R. (2019, February 14). Chemistry 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/books/chemistry-2e
Research Article: Crystal structure of chloramphenicol-metabolizing enzyme EstDL136 from a metagenome
Date Published: January 15, 2019 Publisher: Public Library of Science Author(s): Sang-Hoon Kim, Pyeoung-Ann Kang, Keetae Han, Seon-Woo Lee, Sangkee Rhee, Monika Oberer. http://doi.org/10.1371/journal.pone.0210298 Abstract: Metagenomes often convey novel biological activities and therefore have gained considerable attention for use in biotechnological applications. Recently, metagenome-derived EstDL136 was found to possess chloramphenicol (Cm)-metabolizing features. Sequence analysis showed … Continue reading
Date Published: January 21, 2014 Publisher: Public Library of Science Author(s): Jeffrey Kunkel, Prashanth Asuri, Pratul K. Agarwal. http://doi.org/10.1371/journal.pone.0086785 Abstract: Research over the past few decades has attempted to answer how proteins behave in molecularly confined or crowded environments when compared to dilute buffer solutions. This information is vital to understanding in vivo protein behavior, … Continue reading
Date Published: April 24, 2012 Publisher: Public Library of Science Author(s): Christopher A. Johnston, Chris Q. Doe, Kenneth E. Prehoda, Zhe Zhang. http://doi.org/10.1371/journal.pone.0036014 Abstract: Membrane Associated Guanylate Kinases (MAGUKs) contain a protein interaction domain (GKdom) derived from the enzyme Guanylate Kinase (GKenz). Here we show that GKdom from the MAGUK Discs large (Dlg) is a phosphoprotein … Continue reading
Date Published: July 27, 2010 Publisher: Public Library of Science Author(s): Richard Robinson Abstract: None Partial Text: Calcium signaling is central to many of the most important cellular processes, from intracellular transport to memory. In most cases, calcium first joins up with a protein intermediary, calmodulin. With calcium on board, calmodulin (now called Ca2+/CaM) can … Continue reading