Enzyme Kinetics: Properties of $-Galactosidase
Preparation for Laboratory: Web Tutorial 4, Beta Galactosidase - submit answers to questions
Additonal background: Freeman, “Proteins” pp 51-54 and Box 3.3 pp56-57,
This week, you will begin your investigation of the activity of an enzyme, $-galactosidase,
by using spectroscopy. The power of the techniques that you will use will become obvious when
you calculate how many reactions a single molecule of $-galactosidase catalyzes in a minute. At
the end of the lab, you and your lab partners will design an experiment to be done next week on $-
galactosidase, based on what you have learned this week. The same general techniques that you use
this week will be used for the next two weeks, so what you learn in lab this week will help your
Chemical reactions are at the heart of all biological processes. The body must regulate
precisely all the chemical reactions going on in order to maintain life. Much of this regulation is
done by changing the activity of enzymes, which are biological catalysts.
A catalyst is any substance that speeds the rate of a chemical reaction. Many biological
reactions will progress in the absence of a catalyst, but their speed will be too slow to maintain life.
Let's take a look at a hypothetical reaction in which
A + B <=> C + D
The reaction will eventually reach an equilibrium, that can be described by an equilibrium
constant, Keq. For the above reaction,
Keq = ------------------------
whereby [A], [B], [C] and [D] are the concentrations of A, B, C and D at equilibrium.
This hypothetical reaction may take hours or even days or years to reach equilibrium, but the
presence of a catalyst can speed the reaction by many orders of magnitude such that equilibrium is
reached in much less time. However, the presence of a catalyst does not change the Keq of a
chemical reaction, only the speed at which equilibrium is reached.
Today, you will be looking at the char