91影视

What properties distinguish enzymes from other catalysts?

The covalent catalytic mechanism of an enzyme depends on a single active site Cys whose pK is 8. A mutation in a nearby residue alters the microenvironment so that this pK increases to 10. Would the mutation cause the reaction rate to increase or decrease? Explain.

What roles do proximity and orientation play in enzymatic catalysis?

Studies at different pH鈥檚 show that an enzyme has two catalytically important residues whose pKs are ~4 and ~10. Chemical modification experiments indicate that a Glu and a Lys residue are essential for activity. Match the residues to their pKs and explain whether they are likely to act as acid or base catalysts.

Why is it unlikely that nonenzymatic catalysts operate by preferentially binding the transition state?

Question: Explain why RNase A cannot catalyze the hydrolysis of DNA

Urease, the first enzyme to be crystallized, is inhibited in the presence of Hg, Cd, or Co ions. What does this information suggest about the catalytic mechanism of urease?

Wolfenden has stated that it is meaningless to distinguish between the 鈥渂inding sites鈥� and the 鈥渃atalytic sites鈥� of enzymes. Explain.

Describe the experimental evidence that鈥檚 upports lysozyme鈥檚 catalysis by acid-base catalysis, covalent catalysis, andtransition state stabilization.

Explain why lysozyme cleaves the artificial substrate ${\left(NAG\right)}_4~4000$fourtimes more slowly than it cleaves${\left(NAG\right)}_6$ .