Purification and Properties of l-erythro-3,5-Diaminohexanoate Dehydrogenase from a Lysine-fermenting Clostridium

A DPN-dependent dehydrogenase catalyzing the oxidative deamination of l-erythro-3,5-diaminohexanoate to 3-keto-5-aminohexanoate was purified about 30-fold from extracts of the lysine-fermenting Clostridium SB4. The best preparations have a specific activity of 34 units per mg and are relatively homogeneous. In the presence of sodium dodecyl sulfate the enzyme has a subunit molecular weight of about 37,000. The most active form of the enzyme is a tetramer of molecular weight about 140,000; at high pH or in solutions of low ionic strength it dissociates readily to a dimer of molecular weight about 68,000 which appears to be about one-third as active. The enzyme is highly specific with respect to substrate utilization and consequently is useful for the identification and quantitative estimation of l-erythro-3,5-diaminohexanoate and 3-keto-5-amino-hexanoate. The equilibrium of the dehydrogenase reaction is more favorable for amino acid oxidation than are the equilibria of other similar reactions.