Which drugs block the binding site of an enzyme form a substrate?

Inhibitors

The correct answer is option 1. Inhibitors.

Inhibitors: Enzyme inhibitors are molecules that bind to enzymes and decrease their activity. They can block the binding site of an enzyme, preventing the substrate from binding. There are different types of inhibitors, including competitive inhibitors, which bind to the active site of the enzyme (directly blocking the substrate), and non-competitive inhibitors, which bind to a different site but still inhibit enzyme activity.

Other Options:

2. Poisons:

Poisons are substances that can cause harm or death to organisms by interfering with biological processes. While some poisons can act as enzyme inhibitors, not all inhibitors are poisons. Poisons have a broader definition and are not specific to blocking enzyme binding sites. Incorrect for the specific role of enzyme inhibition described.

3. Messengers:

Messengers typically refer to molecules that transmit signals within or between cells, such as hormones or neurotransmitters. They do not primarily function by blocking enzyme binding sites. Incorrect for the specific role of enzyme inhibition described.

4. Receptors:

Receptors are proteins that bind to specific molecules (ligands), such as hormones or neurotransmitters, and initiate a cellular response. They are not involved in blocking enzyme binding sites. Incorrect for the specific role of enzyme inhibition described.

The correct term for drugs that block the binding site of an enzyme from a substrate is "inhibitors," as they directly interfere with the enzyme's ability to interact with its substrate, thus decreasing or halting the enzyme's activity.