ribonuclease and enzyme kinetics

Question 1

what is turnover number

Answer 1

maximum number of conversions of substrate to product per second for one catalytic site

Question 2

what are the main differences between the lock and key hypothesis and the induced fit theory?

Answer 2

• the lock and key theory suggests that enzyme substrate relations are relatively stable
• the induced fit theory states that the active site may alter to fit the substrate

Question 3

what kinetic changes are associated with competitive inhibition of an enzyme?

Answer 3

same Vmax

higher Km

Question 4

what kinetic changes are associated with non-competitive inhibition of an enzyme?

Answer 4

Vmax decreased

Km unaffected

Question 5

how does ribonuclease degrade RNA?

Answer 5

hydrolyses phosphodiester bonds

Question 6

what evidence is there for the mechanism of ribonuclease?

Answer 6

reaction is pH dependent
use of small molecule inhibitor
use of non-hydrolysable substrate analog
site-directed mutagenesis

Question 7

why is ribonuclease only active around pH 6.5?

Answer 7

histidine residues have pKa of 6.5

Question 8

why can high pH cause hydrolysis of RNA but not DNA?

Answer 8

DNA has no 2’ OH to act as a nucleophile and attack the phosphate