Role of Nγ-Acetyldiaminobutyrate as an Enzyme Stabilizer and an Intermediate in the Biosynthesis of Hydroxyectoine

摘要: Strain CHR63 is a salt-sensitive mutant of the moderately halophilic wild-type strain Halomonas elongata DSM 3043 that affected in ectoine synthase gene (ectC). This accumulates large amounts Ngamma-acetyldiaminobutyrate (NADA), precursor (D. Canovas, C. Vargas, F. Iglesias-Guerra, L. N. Csonka, D. Rhodes, A. Ventosa, and J. Nieto, Biol. Chem. 272:25794-25801, 1997). Hydroxyectoine, ectoine, glucosylglycerate were also identified by nuclear magnetic resonance (NMR) as cytoplasmic organic solutes this mutant. Accumulation NADA, hydroxyectoine, was osmoregulated, whereas levels decreased at higher salinities. The effect growth stage on accumulation investigated. NADA purified from shown to protect thermolabile enzyme rabbit muscle lactate dehydrogenase against thermal inactivation. stabilizing greater than or potassium diaminobutyrate. A (1)H NMR analysis accumulated mutants CHR62 (ectA::Tn1732) (ectC::Tn1732) indicated H. can synthesize hydroxyectoine two different pathways-directly via an alternative pathway converts into without involvement ectoine.