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A new cyclic amino acid was detected in a deletion mutant of the moderately halophilic bacterium Halomonas elongata deficient in ectoine synthesis. Using mass spectroscopy (MS) and nuclear magnetic resonance (NMR) techniques, the substance was identified as 5-amino-3,4- dihydro-2H-pyrrole-2-carboxylate (ADPC). We were able to demonstrate that ADPC is the product of a side reaction of lone ectoine synthase (EC 4.2.1.108), which forms ADPC by cyclic condensation of glutamine. This reaction was shown to be reversible. Subsequently, a number of ectoine derivatives, in particular 4,5-dihydro-2-methylimidazole-4- carboxylate (DHMICA) and homoectoine, were also shown to be cleaved by ectoine synthase, which is classified as a hydro-lyase. This study thus reports for the first time that ectoine synthase accepts more than one substrate and is a reversible enzyme able to catalyze both the intramolecular condensation into and the hydrolytic cleavage of cyclic amino acid derivatives. As ADPC supports growth of bacteria under salt stress conditions and stabilizes enzymes against freezethaw denaturation, it displays typical properties of compatible solutes. As ADPC has not yet been described as a natural compound, it is presented here as the first man-made compatible solute created through genetic engineering.

Item Type:	Refereed Article
Keywords:	Halomonas elongata . Ectoine synthase . ADPC . Genetic engineering . Cyclic amino acid derivatives . Compatible solute
Research Division:	Biological Sciences
Research Group:	Microbiology
Research Field:	Bacteriology
Objective Division:	Health
Objective Group:	Public health (excl. specific population health)
Objective Field:	Food safety
UTAS Author:	Davies, NW (Associate Professor Noel Davies)
ID Code:	70083
Year Published:	2011
Web of Science® Times Cited:	16
Deposited By:	Central Science Laboratory
Deposited On:	2011-05-31
Last Modified:	2017-11-06
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