chapter 13 section 7

Question 1

Are all enzymes proteins?

Answer 1

No. While most enzymes are proteins, some antibodies have catalytic activity, and catalytic RNAs (ribozymes) can also act as enzymes.

Question 2

What are ribozymes?

Answer 2

RNA molecules that act as enzymes

Question 3

What is self-splicing in ribozymes?

Answer 3

Some introns in rRNA or mRNA can excise themselves from RNA transcripts and ligate exons without proteins,

Question 4

What ribozyme catalyzes peptide bond formation in protein synthesis?

Answer 4

The large rRNA of the ribosome’s

Question 5

How does the ribosome catalyze peptide bond formation?

Answer 5

It positions peptidyl-tRNA and aminoacyl-tRNA substrates so the α-amino group attacks the carbonyl C of the peptidyl-tRNA,

Question 6

Why is the discovery of ribozymes significant evolutionarily?

Answer 6

Supports the idea of an ancient RNA world before DNA and proteins.

Question 7

What are catalytic antibodies?

Answer 7

Antibodies (immunoglobulins) that have enzymatic activity; also called abzymes.

Question 8

How are abzymes produced experimentally?

Answer 8

By immunizing an organism with a transition-state analog of a reaction; the resulting antibody binds the transition state and catalyzes the reaction.

Question 9

How can catalytic antibodies accelerate ester hydrolysis?

Answer 9

By eliciting antibodies against a phosphonate analog of the transition state, which can increase the rate of ester hydrolysis up to 1000-fold.

Question 10

Can catalytic antibodies occur naturally? Give examples.

Answer 10

Yes; in autoimmune diseases like multiple sclerosis, antibodies can degrade myelin basic protein

Question 11

What other reactions have abzymes been designed to catalyze?

Answer 11

C–C bond formation via aldol condensation and pyridoxal 5′-P–dependent aminotransferase reactions

Question 12

What principle explains the catalytic power of abzymes?

Answer 12

Their affinity for the transition state of a reaction facilitates substrate conversion to the transition-state conformation.