This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Vit K is needed for which of these posttranslational modification processes \nSelect and explain. \nA. Methylation, B. Carboxylation, C. Hydroxylation, D. Transketolation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Vitamin K functions as a cofactor for an enzyme carboxylase that catalyzes post-translation modification by carboxylation of glutamic acid (glutamate) residues on vitamin K dependent proteins.', 'role': 'assistant'}]