## Core Concept
Non-competitive inhibition is a type of enzyme inhibition where the inhibitor binds to a region of the enzyme outside of the active site, called the allosteric site. This type of inhibition reduces the activity of the enzyme without affecting the substrate binding.

## Why the Correct Answer is Right
In non-competitive inhibition, the inhibitor binds to the enzyme-substrate complex or the free enzyme at an allosteric site, changing the shape of the enzyme and affecting its ability to convert substrate to product. This type of inhibition cannot be overcome by increasing the substrate concentration.

## Why Each Wrong Option is Incorrect
* **Option A:** Increasing the substrate concentration does not affect the inhibition, which is a characteristic of non-competitive inhibition.
* **Option B:** The inhibitor binds to an allosteric site on the enzyme, which is a defining feature of non-competitive inhibition.
* **Option C:** Non-competitive inhibition reduces the maximum velocity (Vmax) of the enzyme reaction without affecting the Michaelis constant (Km), which is a measure of the affinity of the enzyme for the substrate.

## Clinical Pearl / High-Yield Fact
A key point to remember is that non-competitive inhibitors can be either reversible or irreversible. Reversible non-competitive inhibitors can be displaced by high concentrations of substrate, but irreversible inhibitors form covalent bonds with the enzyme and cannot be displaced.

## Correct Answer: D.