PT  - JOURNAL ARTICLE
AU  - Khomyakova, Maria
AU  - Bükmez, Özlem
AU  - Thomas, Lorenz K.
AU  - Erb, Tobias J.
AU  - Berg, Ivan A.
TI  - A Methylaspartate Cycle in Haloarchaea
AID  - 10.1126/science.1196544
DP  - 2011 Jan 21
TA  - Science
PG  - 334--337
VI  - 331
IP  - 6015
4099  - http://science.sciencemag.org/content/331/6015/334.short
4100  - http://science.sciencemag.org/content/331/6015/334.full
SO  - Science2011 Jan 21; 331
AB  - Access to novel ecological niches often requires adaptation of metabolic pathways to cope with new environments. For conversion to cellular building blocks, many substrates enter central carbon metabolism via acetyl–coenzyme A (acetyl-CoA). Until now, only two such pathways have been identified: the glyoxylate cycle and the ethylmalonyl-CoA pathway. Prokaryotes in the haloarchaea use a third pathway by which acetyl-CoA is oxidized to glyoxylate via the key intermediate methylaspartate. Glyoxylate condensation with another acetyl-CoA molecule yields malate, the final assimilation product. This cycle combines reactions that originally belonged to different metabolic processes in different groups of prokaryotes, which suggests lateral gene transfer and evolutionary tinkering of acetate assimilation. Moreover, it requires elevated intracellular glutamate concentrations, as well as coupling carbon assimilation with nitrogen metabolism.