This work describes, with some detail the intervention of 4-aminobutyrate as protagonist of a derivation of tricarboxylic cycle. Its vicarial mission is emphasized in connection with its existence in microorganisms (Escherichia coli and Pseudomonas fluorescens), plants (Helianthus tuberosus. Lupinus albus and Agave americana), neoplasic cells (ascitic tumor of Ehrlich and HeLa cells) and animal tissues (adrenal medulla and brain.