The Important Role of Halogen Bond in Substrate Selectivity of Enzymatic Catalysis

Abstract

The use of halogen bond is widespread in drug discovery, design, and clinical trials, but is overlooked in drug biosynthesis. Here, the role of halogen bond in the nitrilase-catalyzed synthesis of ortho-, meta-, and para-chlorophenylacetic acid was investigated. Different distributions of halogen bond induced changes of substrate binding conformation and affected substrate selectivity. By engineering the halogen interaction, the substrate selectivity of the enzyme changed, with the implication that halogen bond plays an important role in biosynthesis and should be used as an efficient and reliable tool in enzymatic drug synthesis.

Figure 1

(A) The nitrilase substrate selectivity of ortho-, meta-, and para-isomers, (B) Proposed nitrilase reaction mechanism.

Figure 2. The surface of 1a, 1b and 1c in the binding pocket of WT.

1a, 1b and 1c are shown in green, cyan and orange (A). And the halogen bonds and aromatic interactions in complexes: WT-1a (B), WT-1b (C), T54Y-1b (D), WT-1c (E), H141W-1c (F). Key residues are presented as ball and stick with carbon atoms in gray, hydrogen in white, oxygen in red, nitrogen in blue, chloride in green, sulfur in yellow. And loop 139–140 was presented as cartoon in green. The geometric information of halogen bonds in this figure can be accessed in Supporting Information Table S3.

Figure 3. Geometric model of two types of halogen bond, C–X···Y and C–X···π.