Aspirin inhibits which of the following enzymes?
**Core Concept**
Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that exerts its effects by inhibiting an enzyme involved in the synthesis of prostaglandins, which are key mediators of inflammation and pain.
**Why the Correct Answer is Right**
Aspirin specifically targets the enzyme cyclooxygenase (COX), which is responsible for converting arachidonic acid to prostaglandin H2 (PGH2). This is the first step in the synthesis of various prostaglandins, including PGE2, PGF2α, and thromboxane A2. By inhibiting COX, aspirin reduces the production of these prostaglandins, leading to its analgesic, anti-inflammatory, and antiplatelet effects.
**Why Each Wrong Option is Incorrect**
* **Option A:** Glycogen synthase is an enzyme involved in glycogen synthesis and is not related to aspirin's mechanism of action.
* **Option B:** Acetylcholinesterase is an enzyme involved in the hydrolysis of acetylcholine at the neuromuscular junction and is not directly affected by aspirin.
* **Option C:** Lipoxygenase is an enzyme involved in the synthesis of leukotrienes from arachidonic acid, but aspirin's primary mechanism of action is through inhibition of COX, not lipoxygenase.
**Clinical Pearl / High-Yield Fact**
Aspirin's ability to inhibit COX-1 and COX-2 enzymes also contributes to its antiplatelet effects, which are beneficial in preventing myocardial infarction and stroke in patients at high risk.
**Correct Answer:** C. cyclooxygenase (COX)