American Board of Surgery Qualifying Exam (ABS QE) Practice Test 2025 - Free Surgery Exam Practice Questions and Study Guide

The primary substrate for nitric oxide synthase (NOS) in the inflammation process is arginine. This amino acid serves as a crucial building block that NOS utilizes to produce nitric oxide (NO), a key signaling molecule involved in various physiological and pathological processes, including vasodilation, neurotransmission, and immune response during inflammation.

In the context of inflammation, the production of nitric oxide plays an important role in mediating the immune response, helping to regulate blood flow, and promoting various cellular functions. Arginine is converted to citrulline in this reaction, which means that while citrulline is a product of the process, it is not the substrate that initiates the production of nitric oxide.

Other amino acids listed, such as glycine and proline, do not play a direct role as substrates for nitric oxide synthase. Therefore, arginine stands out as the correct answer due to its essential role in the biosynthesis of nitric oxide in inflammatory responses.