8. Which of the following is able to release an ammonium ion? (A) Conversion of hydroxymethylbilane to uroporphyrinogen III by uroporphyrinogen III synthase (B) Conversion of serine to glycine by serine hydroxymethyltransferase (C) Conversion of glutamate to glutamine by glutamine synthetase (D) Conversion of cystathionine to cysteine and α-ketobutyrate by cystathionine γ-lyase