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How do hydrophobic forces help enzymes attract substrates?

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A multi-panel diagram illustrates how a substrate binds to an enzyme's active site through induced fit, leading to product formation, and shows how non-substrates and allosteric regulators can alter enzyme activity by binding to different sites on the enzyme. — Enzyme In the induced-fit theory of enzyme-substrate binding, a substrate approaches the surface of an enzyme (step 1 in box A, B, C) and causes a change in the enzyme shape that results in the correct alignment of the catalytic groups (triangles A and B; circles C and D represent substrate-binding groups on the enzyme that are essential for catalytic activity). The catalytic groups react with the substrate to form products (step 2). The products then separate from the enzyme, freeing it to repeat the sequence (step 3). Boxes D and E represent examples of molecules that are too large or too small for proper catalytic alignment. Boxes F and G demonstrate binding of an inhibitor molecule (I and I′) to an allosteric site, thereby preventing interaction of the enzyme with the substrate. Box H illustrates binding of an allosteric activator (X), a nonsubstrate molecule capable of reacting with the enzyme.

Hydrophobic forces play a critical role in the binding of substrates to enzymes by facilitating the attraction of nonpolar regions between the two molecules. These forces are classified as noncovalent bonds, meaning they are physical attractions rather than chemical bonds.1

Specifically, hydrophobic interactions occur when the oily or hydrocarbon portions of an enzyme and its substrate are forced together. This process is analogous to the way oil droplets tend to coalesce when placed in water. By bringing these hydrophobic regions together, the enzyme helps stabilize the enzyme-substrate complex at the active site, which is a necessary step before catalysis can proceed. These physical attractions, alongside electrostatic forces, ensure that the substrate is properly positioned within the enzyme's active site to allow the chemical reaction to occur.21