Tagatose-1,6-bisphosphate (TBP) aldolase and related Type B Class II aldolases. TBP aldolase is a tetrameric class II aldolase that catalyzes the reversible condensation of dihydroxyacetone phosphate with glyceraldehyde 3-phsophate to produce tagatose 1,6-bisphosphate. There is an absolute requirement for a divalent metal ion, usually zinc, and in addition the enzymes are activated by monovalent cations such as Na+. The type A and type B Class II FBPA's differ in the presence and absence of distinct indels in the sequence that result in differing loop lengths in the structures.
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