PLE-1545

A 4-month-old boy is being evaluated for seizures, psychomotor retardation, and hypotonia. Work-up reveals elevated serum levels of lactate, alanine, pyruvate, and ketoacids. Based on the clinical presentation, pyruvate carboxylase activity is measured using fibroblasts from a skin biopsy and is found to be markedly decreased. This enzyme is normally used to directly synthesize which of the following molecules?