Question

Enolase is an enzyme that catalyzes one reaction in glycolysis in all organisms that carry out this process. The amino acid sequence of enolase is similar but not identical in the organisms. Researchers purified enolase from  Saccharomyces cerevisiae, a single-celled eukaryotic yeast that grows best at  37°C, and from  Chloroflexus aurantiacus, a bacterium that grows best at the much higher temperature of  55°C. The researchers compared the activity of purified enolase from the two organisms by measuring the rate of the reaction in the presence of varying concentrations of substrate and a constant amount of each enzyme at both  37°C and  55°C.

(a) Depending on the organism, the optimal  pH for enolase to catalyze its reaction is between  6.5 and  8.0.  Describe how a  pH below or above this range is likely to affect enolase and its catalytic ability.

Question 2

(b)  Identify the appropriate negative control the researchers most likely used when measuring the reaction rate in the presence of each organism’s enolase.

Question 3

(c) The researchers predict that for any particular concentration of substrate, the  C. aurantiacus enolase-catalyzed reaction is more rapid at  55°C than at  37°C. Provide reasoning to  justify the researchers’ prediction.

Answer 1