Which enzyme is responsible for adding ubiquitin molecules to proteins, marking them for degradation by the proteasome?

A Ubiquitin ligase ✓
B Proteasome
C Deubiquitinase
D Peptidase

Explanation

Ubiquitin ligase is the enzyme responsible for attaching ubiquitin molecules to proteins, targeting them for degradation by the proteasome.

Source

Harper's Illustrated Biochemistry
Protein Metabolism Cell Biology Protein Degradation Hard MEDICAL Confidence: high