The biosynthesis of ectoine

The biosynthetic pathway of the novel compatible solute ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) was studied in the two extremely halophilic eubacteria Ectothiorhodospira halochloris and Halomonas elongata. The pathway starts with the phosphorylation of l-aspartate and shares its first two enzymatic steps with the biosynthesis of amino acids of the aspartate family: aspartokinase and l-aspartate-β-semialdehyde dehydrogenase. Evidence is presented for the presence of the enzymes l-diaminobutyric acid transaminase and l-diaminobutyric acid acetyl transferase and for the new enzyme the ring-forming ectoine synthase.