Chapter 1 Why Purify Enzymes?

Don't waste clean thinking on dirty enzymes" is an admonition of Efraim Racket's which is at the core of enzymology and good chemical practice. It says simply that detailed studies of how an enzyme catalyzes the conversion of one substance to another is generally a waste of time until the enzyme has been purified away from the other enzymes and substances that make up a crude cell extract. The mixture of thousands of different enzymes released from a disrupted liver, yeast, or bacterial cell likely contains several that direct other rearrangements of the starting material and the product of the particular enzyme's action. Only when we have purified the enzyme to the point that no other enzymes can be detected can we feel assured that a single type of enzyme molecule directs the conversion of substance A to substance B, and does nothing more. Only then can we learn how the enzyme does its work.