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The three-dimensional structure of L-fuculose-1-phosphate aldolase (FucA) from
Escherichia coli was determined by X-ray crystallography at a resolution of 2.13
A. The enzyme is a homotetramer with an M(r) of 23,775 per subunit. Since its
activity depends on the presence of metal ions (Zn2+) the enzyme belongs to the
class II aldolases. As expected from amino acid sequence comparisons, this first
structure of a class II aldolase shows no similarity to the known structures of
class I aldolases. It has some unusual features concerning the overall chain
fold, the quaternary structure, and the co-ordination of the catalytically
active zinc ion. A sequence comparison with the data bank indicated that the
middle domain of the enzyme L-ribulose-5-phosphate-4-epimerase is homologous to
FucA and may contain an active-center metal ion.
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