Chemistry in Water

What do enzymes have to do with it anyway?





Enzymes are specialized proteins that have a unique shape and chemical composition that creates a site, called and active site, for connection between the enzyme and other molecules called substrates.  The shape and chemical makeup of the active site provides an area for part of the substrate to connect with the enzyme. Part of the active site holds the substrate and part catalyzes the reaction.  The active site binds the substrate based on many chemical factors including shape, stereochemistry, electrical charge, and hydrophilic/hydrophobic considerations.  The enzyme and substrate fit together through an induced fit, where the active site must have complimentary structures to those of the substrate to allow binding.   The substrate is held in a position that is energetically favorable for the reaction to take place.  The enzyme aids the process by allowing the reaction to occur at a faster rate and with lower energy requirements than under non-enzyme conditions.  In this way, enzymes act as catalysts for biochemical reactions.  Each enzyme is capable of catalyzing reactions with many successive substrate molecules without itself being consumed during the reactions.  The pictures above and below are representations of the enzyme papain which comes from papaya.  Notice that the representation below highlights the active site. 

In this lab, you will look at the reaction between the enzymes, a-amylase and amyloglucosidase, and the substrate starch.  These reactions are important for the digestion of starches.  Starch is a macromolecule made up of bonded saccaride molecules.  These saccaride molecules are biologically useful, often as a source of energy.  When the component molecules bond to form the polymer we call starch, a water molecule is eliminated at each bond.  This type of polymerization is called dehydration polymerization.  Amylase is an enzyme that catalyses the breakdown of starches into component molecules by allowing a water molecule to rehydrate the bonds in a process called hydrolysis.  The water molecule splits to add hydroxide (OH) to one side of the bond and hydrogen to the other side.   Amylase is found in the saliva and lower intestine of all mammals and in the digestive tract of most animals.  It can also be found in some plants where it is used to breakdown stored starch, and it can be found in fungi and bacteria that attack plants.  Amyloglucosidase is an enzyme similar to amylase, which only occurs in fungi and bacteria.

 Background Resources


This site contains a model of the enzyme papain (derived from papaya).

This site contains the entry on enzymes in Encarta.  The site provides some background information on enzymes and how they work.

This site contains background information and links to more in-depth discussion of enzymes from a biomedical corporation, Worthington Biomedical Corporation.  Written for students and teachers.

This site contains a brief description of some of the energetics of enzymes.  This site comes from the KU Microbiology Department.

The following sites contain more detailed information about enzyme bonding and structure.