A 25-year-old woman develops a sore, red, hot, swollen left knee. She has no history of trauma and no familial history of joint disease .Aspirin is effective in relieving symptoms of acute inflammation in this patient because it inhibits which of the following enzymes?

Arachidonic acid is metabolized by cyclooxygenases (COX-1, COX-2) and lipoxygenases (5-LOX) to generate prostanoids and leukotrienes, respectively. The early inflammatory prostanoid response is COX-1 dependent. COX-2 becomes the major source of prostanoids as inflammation progresses. Inhibition of COX is one mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, indomethacin and ibuprofen, exe their potent analgesic and anti-inflammatory effects. NSAIDs block both COX-1 & COX-2 induced formation of prostaglandins, thereby mitigating pain and inflammation.