Overlay of regions of the active sites of pyruvate decarboxylase from Zymomonas mobilis (gold) and benzoylformate decarboxylase (green) from Pseudomonas putida. In addition to the cofactor, thiamine diphosphate and the magnesium ion which are orientated in very similar positions in both enzymes, two of the amino acid residues which help determine the substrate range of each enzyme are shown. Site-directed mutagenesis was used to alter the enzymes' specificities by interchanging these residues. For details, see Siegert et al., pages 345–357. (The image was created using the program QUANTA.)
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