Characterization of a novel type homoserine dehydrogenase with high oxidation activity from Arthrobacter nicotinovorans

Homoserine dehydrogenase (HSD) is a key enzyme in the synthesis pathway of the aspartate family of amino acids. HSD can catalyze the reversible reaction of l-aspartate-β-semialdehyde (l-Asa) to l-homoserine (l-Hse). In this study, one putative homoserine dehydrogenase from Arthrobacter nicotinovorans, which was named AnHSD, was different from those HSDs that from the aspartic acid metabolic pathway, and might be responsible for the specific oxidation of l-Hse. Surprisingly, the analysis showed that the purified AnHSD exhibited high oxidation activity of l-Hse. At pH 10.0 and 40 °C, the Km and kcat of AnHSD was 5.97 ± 1.10 mM and 3.61 s−1, respectively. In terms of cofactor reliance, AnHSD preferred NAD+ than NADP+ as a cofactor. The physiological role of AnHSD under natural pH is also discussed in A. nicotinovorans. Collectively, these findings provide a novel insight for a better understanding of a novel HSD, and a possible biotransformation method for preparing l-Asa.