Escherichia coli (LacZ)
As you proceed through this tutorial buttons must be activated in sequence to work
correctly. If you want to redo the tutorial RELOAD the program.
Beta galactosidase the molecule rotating on the left is an enzyme that initiates the
breakdown of the sugar lactose. Lactose is a type of sugar found in milk. It is composed of two
rings. The rings contain 5 carbon atoms, one at each corner (not shown) and an oxygen
Attached to the carbon atoms are a hydrogen atom (not shown --) and an OH group or
another carbon (C).
The rings are bound together by an oxygen bridge. This bridge can be broken when the enzyme
beta galactosidase binds to lactose and a water molecule reacts with the oxygen atom in the bridge. Reactions
in which water molecules are added are known as hydrolysis reactions.
The beta galactosidase you will be using in lab this week was isolated from the bacteria
Escherichia coli. This bacteria produces beta galactosidase when lactose is present in its growth
II. General Structure of Beta Galactosidase Complexed with Lactose
The structure of the molecule on the left was determined using X-ray diffraction techniques.
It is a homotetramer meaning that it is composed of four identical chains of amino acids. Click the button
to more clearly see each chain. <