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. Author manuscript; available in PMC: 2014 Aug 1.
Published in final edited form as: Curr Opin Chem Biol. 2013 Jul 17;17(4):580–588. doi: 10.1016/j.cbpa.2013.06.018

Figure 4.

Figure 4

Overview of phosphonate catabolism. (a) Gene cluster of the Phn operon for reductive C-P bond cleavage. (b) Schematic overview of the C-P lyase pathway. (c) A recently proposed mechanism for PhnJ catalyzed C-P bond cleavage [38]. The cube represents the [4Fe-4S] cluster. (d) Phosphonoacetate hydrolase (PhnA) is a newly discovered hydrolase that takes advantage of the carboxylate group as a "β electron sink". (e) Phosphonatase is able to convert 2-AEP to free phosphate through PnAA. (f) PnPy hydrolase is used to liberate phosphate from PnPy after transamination of PnAla. (g) The two lysines (shown as sticks) in the PhnA-T68A active site are relatively far from PnA. Ala68 is set up for in-line attack on the phosphonate when this residue is Thr in wild type PhnA, and the π-system of the carboxylate of PnA is well oriented to accept electron density upon cleavage of the P-C bond. The incipient negative charge may also be stabilized by binding to a Zn(II) in a monodentate fashion. (h) A recently discovered pathway from a genomic marine library results in oxidative cleavage of the C-P bond.