Enzyme prochiral substrate, binding

We can understand this result by imagining that the chiral enzyme receptor again has three binding sites, as was previously the case in Figure 9.17. When green and gray substituents of a prochiral substrate are held appropriately, however, only one of the two red substituents—say, the pro-S one— is also held while the other, pro-R, substituent is exposed for reaction. 

Case V There is a good binding of a prochiral substrate (C) to the complementary enzyme s binding sites with the pro-(/ ) group out of the two reactive groups (A) being positioned towards the chemical operator. 

Fig. 2.9. A model for binding of a prochiral substrate (ethanol) by an enzyme...

FIGURE 17 14 (a) Binding sites of enzyme discriminate between prochiral faces of substrate One prochiral face can bind to the enzyme better than the other (b) Reaction attaches fourth group to substrate producing only one enantiomer of chiral product... 

It was not until 1948 that Ogston popularized the concept that by binding with substrates at three points, enzymes were capable of asymmetric attack upon symmetric substrates.d In other words, an enzyme could synthesize citrate with the carbon atoms from acetyl-CoA occupying one of the two -CH2COOH groups surrounding the prochiral center. Later, the complete stereochemistry of the... 

It was pointed out over 60 years ago that the recognition of a chiral (or, as subsequently realized, a prochiral) carbon by an enzyme implies that at least three of the groups surrounding the carbon atom must interact with the enzyme. This is the multi-point attachment theory.4 If only two of the groups interact, the other two may be interchanged without affecting the binding of the substrate (structures 8.9). 

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