Homoserine dehydrogenase signature

Homoserine dehydrogenase (EC 1.1.1.3) (HDh) [1,2] catalyzes NAD-dependent reduction of aspartate β-semialdehyde into homoserine. This reaction is the third step in a pathway leading from aspartate to homoserine. The latter participates in the biosynthesis of threonine and then isoleucine as well as in that of methionine.

HDh is found either as a single chain protein as in some bacteria and yeast, or as a bifunctional enzyme consisting of an N-terminal aspartokinase domain and a C-terminal HDh domain as in bacteria such as Escherichia coli and in plants.

As a signature pattern, we selected the best conserved region of Hdh. This is a segment of 23 to 24 residues located in the central section and that contains two conserved aspartate residues.