76. Which one of the following statements is NOT correct?
(A) Δ¹-Pyrroline-5-carboxylate serves as a key intermediate in both L-proline synthesis and breakdown pathways.
(B) Human cells synthesize non-essential amino acids using intermediates from central metabolic pathways or by converting essential amino acids.
(C) Phenylalanine hydroxylase catalyzes the interconversion between phenylalanine and tyrosine.
(D) Liver cells produce serine starting from the glycolysis product 3-phosphoglycerate.
(E) NADPH provides the ultimate source of reducing equivalents for tetrahydrobiopterin regeneration.