The transition state for enzyme-catalyzed pyrophosphate hydrolysis, deduced from the structure of the enzyme inorganic pyrophosphatase, is shown in Fig. 25.6.

(a) Indicate the catalytic role of each numbered feature—that is, how each feature enhances catalysis.

(b) If the stereochemistry of the reaction could be determined by isotopic and sulfur substitution of the oxygens, would the result be retention or inversion of configuration at phosphorus?

Transcribed Image Text:

protein 2 Mg²+ H Mg²+ glutamic acid (Glu) residue tyrosine (Tyr) residue protein 0: H Mg²+ Mg2+ 2 H & O& -H-N H-N H H protein arginine (Arg) residue FIGURE 25.6 The active site for pyrophosphate hydrolysis catalyzed by yeast inorganic pyro- phosphatase. (See Problem 25.13.) The groups in blue are from amino acid residues (identified in parentheses) of the protein in the active site. The numbers refer to aspects of catalysis to be iden- tified when working the problem.