Final answer:
The coenzyme required for the reduction of β-aspartate-semialdehyde to homoserine is NADH, which acts as a hydride donor in this amino acid biosynthesis reaction.
Step-by-step explanation:
The coenzyme needed in the conversion of β-aspartate-semialdehyde to homoserine, which is a reduction reaction, is NADH. This reaction is part of amino acid biosynthesis, where the aldehyde group of β-aspartate-semialdehyde is reduced to a hydroxyl group to form homoserine. NADH acts as a hydride donor, providing the necessary hydrogen atoms to facilitate this reduction, becoming oxidized to NAD+ in the process. While FAD and FADH2 are important coenzymes in various oxidation-reduction reactions, in this specific case, it is NADH that is required to drive the reaction forward.