An enzyme inhibitor is a substance that decreases the activity of an enzyme, which is a protein that speeds up chemical reactions in the body. By binding to the enzyme, the inhibitor can prevent it from functioning properly, which can affect various biological processes. Enzyme inhibitors can be naturally occurring or synthetic and are often used in medicine to treat diseases by slowing down specific biochemical reactions. There are two main types of enzyme inhibitors: competitive and non-competitive. Competitive inhibitors resemble the enzyme's natural substrate and compete for the active site, while non-competitive inhibitors bind to a different part of the enzyme, altering its shape and function. Understanding enzyme inhibitors is crucial in fields like pharmacology, where they are used to design drugs that target specific enzymes related to diseases.