| Comment | This HMM represents a clade of sequences related to fructose-bisphosphate aldolase (class I, included within PF01791). The members of this clade appear to be phospho-2-dehydro-3-deoxyheptonate aldolases. This enzyme is the first step of the chorismate biosynthesis pathway. Evidence for this assignment is based on gene clustering and phylogenetic profiling.
A group of species lack members of the three other types of phospho-2-dehydro-3-deoxyheptonate aldolase (represented by TIGR00034, TIGR01358 and TIGR01361), and also aparrently lack the well-known forms of step 2 (3-dehydroquinate synthase), but contain all other steps of the pathway: Desulfovibrio, Aquifex, Archaeoglobus, Halobacterium, Methanopyrus, Methanococcus and Methanobacterium. The clade of sequences represented here is limited strictly to this group of organisms.
In Desulfovibrio, Aquifex, Archaeoglobus, Halobacterium and Methanosarcina the genes found by this model are clustered with other genes from the chorismate, phenylalanine, tyrosine and tryptophan biosynthesis pathways.
In addition, these genes in Desulfovibrio, Archaeoglobus, Halobacterium, Methanosarcina and Methanopyrus are adjacent to a gene which hits PF01959 which also has the property of having members only in those species which lack steps 1 and 2.
Together these two genes appear to perform the synthesis of 3-dehydroquinate. It is presumed that the substrates and the chemical transformations involved are identical, but this has not yet been proven experimentally. |
