This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor.

Homoserine dehydrogenase has an NAD(P)H cofactor, which then donates a hydrogen to the same carbon, effectively reducing the aldehyde to an alcohol.

[11] Homoserine dehydrogenase catalyzes an intermediate step in this nitrogen and carbon storage and utilization pathway.

[12] Additionally, the aspartate kinase-homoserine dehydrogenase gene is primarily expressed in actively growing, young plant tissues, particularly in the apical and lateral meristems.

[13] Mammals lack the enzymes involved in the aspartate metabolic pathway, including homoserine dehydrogenase.

As lysine, threonine, methionine, and isoleucine are made in this pathway, they are considered essential amino acids for mammals.

[14] In AK-HSD expressing organisms, one of the threonine binding sites is found in the linker region between AK and HSD, suggesting potential allosteric inhibition of both enzymes.

[6] However, some threonine-resistant HSD forms exist that require concentrations of threonine much greater than physiologically present for inhibition.

These threonine-insensitive forms of HSD are used in genetically engineered plants to increase both threonine and methionine production for higher nutritional value.

[12][13] In humans, there has been a significant increase in disease from pathogenic fungi, so developing anti-fungal drugs is an important biochemical task.

[15] As homoserine dehydrogenase is found mainly in plants, bacteria, and yeast, but not mammals, it is a strong target for antifungal drug development.