Structure of ACL Racemase

Overall structure of ACL racemase complexed with e-caprolactam (e-cl, ball and stick representation). PLP and Lys267 are represented as ball and stick. Hydrogen bond Is represented as broken line. 

In the crystalline state, two subimit molecules in the as5mimetric unit formed a tightly packed homodimer (a contact area of 4000A) stabilized by 48 interchain hydrogen bonds. This long list imderscores the strength of the intersubunit interactions in this dimer and indicates that ACL racemase forms a dimer in solution similar to other fold-t) e 1 enz3mies [13]. 

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The crystal structures of the apo form and e-caprolactam complexed form of ACL racemase were solved at resolutions 2.21 A and 2.40 A, respectively [26]. The structure of ACL racemase was found to be composed of an N-terminal domain (residues 3 3), C-terminal domain (residues 321 36), and large PLP-binding domain (residues 48-319) (Figure 19.6). PLP boimd in a cleft between these domains, and the C4 atom of PLP connected covalently to the e-amino group of Lys267 to form the internal aldimine (Schiff base) linkage. 

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