Final answer:
Biotin-dependent enzymes are required for carboxylation reactions and attach biotin to metabolic proteins involved in carboxylation or decarboxylation. These enzymes use carbonate as the source of the carboxyl group and require ATP and Mg²+.
Step-by-step explanation:
Biotin-dependent enzymes are required for carboxylation reactions in living organisms. These enzymes use carbonate (HCO,B) as the source of the carboxyl group and ATP to activate it. Mg²+ is also needed to decrease the overall negative charge. Biotin is attached to lysine residues of metabolic proteins involved in carboxylation or decarboxylation. Some examples of biotin-containing proteins are acyl-CoA carboxylase and birA protein ligase.