Activities of Bacterial Enzymes
Enzymes are the most important chemical mediators of every living cell’s activities. These organic
substances catalyze, or promote, the uptake and use of raw materials needed for synthesis of cellular
components or for energy. Enzymes are also involved in the breakdown of unneeded substances
or of metabolic side products that must be eliminated from the cell and returned to the
As catalysts, enzymes promote changes only in very specific substances or substrates, as
they are often called. Thus, in the previous exercise, the changes produced in simple carbohydrates
and in starch substrates were brought about by different, specific enzymes. We have seen the activity
of an enzyme with a different kind of outcome, the breakdown of an antimicrobial agent (see
Experiment 15.3), but the principle is exactly the same.
In the latter instance, the beta-lactamase
enzyme penicillinase brought about a change in the substrate penicillin.
Since enzymes appear to be limited to particular substrates, it follows that each bacterial
cell must possess a large battery of different enzymes, each mediating a different metabolic
process. They are identified in terms of the type of change produced in the substrate. In naming
them, the suffix -ase is usually added to the name of the substrate affected. Thus, urease is an enzyme
that degrades urea, gelatinase breaks down gelatin (a protein), penicillinase inactivates penicillin,
and so on.
In this exercise, we shall see how many bacterial enzymes are demonstrated and how
their recognition in bacterial cultures leads to identification of species.