R Is for Arginine

D ow nloaded from DOI: 10.1161/CIRCULATIONAHA.113.005924 2 First published in 1962, Ray Bradbury’s short story collection “R is for Rocket ” provided a view of space travel with a prescience and sophistication that transformed the simpler notions of the time. And in a simpler era dating back only to the mid-1980s, L-arginine (abbreviated R in the single letter amino acid code) seemed to be just another amino acid, notable principally for its guanido group, which conferred arginine with a high pK and provided its distinction as one of the three basic amino acids. Abundant in many types of food, synthesized from simple precursors, or recycled in different tissues in the body, arginine is classified as a non-essential amino acid: except under extreme conditions, nutritional states of arginine deficiency are rare. Yet how much more complicated and interesting has arginine become in the past three decades! The role of arginine as a humdrum amino acid was forever transformed by the discovery that thi