Microbial Metabolism Practice Test

The key idea is that certain enzymes specialize in breaking the bonds within nucleic acids, which are DNA and RNA. Nucleases do exactly that: they hydrolyze the phosphodiester bonds linking nucleotides, either cutting within the strand (endonucleases) or trimming from the ends (exonucleases). Many nuclease reactions require divalent metal ions like magnesium or manganese to help water attack the phosphodiester bond, enabling cleavage. This is the activity you’d see in processes such as DNA digestion, RNA degradation, or roles in DNA repair and restriction systems. Proteases break peptide bonds in proteins, not nucleic acids. Lipases hydrolyze ester bonds in lipids, not the sugar-phosphate backbone. Glycosidases cleave glycosidic bonds in carbohydrates, not nucleic acids. So the enzyme class that cleaves nucleic acids is nucleases.