Converts glucosinolates both to epithionitriles and to simple nitriles in the presence of myrosinase. Promotes the formation of epithionitriles after hydrolysis of alkenylglucosinolates containing a terminal double bond. Mediates indol-3-acetonitrile (IACN) production from indol-3-ylmethyl glucosinolate. Acts as a negative regulator of senescence. Interacts with WRKY53. Brought to the nucleus after interaction with WRKY53. Expressed in epidermal cells of all above-ground organs except the anthers, in cambial cells of leaf and stem vascular bundles, and in glucosinolates rich S-cells found in stems just below the inflorescence. Absent from roots. By jasmonate. Accelerated leaf senescence and increased pathogen damages. ESP is functional in cv. Landsberg erecta while the gene encoding the protein is not expressed in cv. Columbia, cv. Da(1)-12 and cv. Ru-0. ESP activity is regulated at the transcriptional, the post-transcriptional and the post-translational levels. Not dependent on the presence of Fe(2+) although supplemental Fe(2+) increases nitriles formation.