The Active site on Fructose 1,6-Bisphosphatase contains three metal atoms which mediate the enzymatic reaction. The site is active if these metals bound are Zinc+ atoms and inhibited if these sites are bound to Lithium. As you can see here, the 3 Zinc atoms bind to the enzyme and show the vauge picture of a binding site :

• Zn "1" is held in place by glutamic acid 97 .
• Zn "2" is held in place with "partner" peptides Glutamic acid 280 and its trusty sidekick, aspartic acid 118.
• Zn "3" is bound to glutamic acid 97, just like its friend Zinc "1."

The Three Zinc atoms inturn bind an inorganic phospate on the incoming fructose 1,6-bisphosphate and make it fructose 6-phosphate (what a good enzyme, prrrrrrrr). This reaction is regulated by fructose 2,6-bisphosphotase which binds competitively with the active site.

Allosteric Regulation:

Fructose 1,6-bisphosphatase is allosterically controlled by the binding of AMP to a currently undefined site which causes the loop 52-72 to change conformation. The molecule is active when the loop is in its R-state, and inhibited when in its T-state. Here the loop is shown with the active site. As you can see, the loop and the active site are fairly close in proximity but not directly connected. For a schematic of the mechanism for allosteric regulation, click here.

To see the active site within a gaussian surface representation, click here:

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