Aldolases of the DhnA family: a possible solution to the problem of pentose and hexose biosynthesis in archaea

Sequence analysis of the recently identified class I aldolase of Escherichi a coli (dhnA gene product) helped to identify its homologs in Chlamydia tra chomatis, Chlamydiophyla pneumoniae and in each of the completely sequenced archaeal genomes. Iterative database searches revealed sequence similariti es between the DhnA-family enzymes, deoxyribose phosphate aldolases and bac terial (class II) fructose bisphosphate aldolases and allowed prediction of similar three-dimensional structures (TIM-barrel fold) in all these enzyme s. The Schiff base-forming lysyl residues of DhnA and deoxyribose phosphate aldolase are conserved in all members of the DhnA and deoxyribose phosphat e aldolase families, indicating that these enzymes share common features wi th both class I and class II aldolases. The DhnA-family enzymes are predict ed to possess an aldolase activity and to play a critical role in sugar bio synthesis in archaea. (C) 2000 Published by Elsevier Science B.V. All right s reserved.