Leukotriene E4 (LTE4) is produced by the action of dipeptidase on LTD4, leaving only the cysteinyl group still attached to the fatty acid backbone. It is one of the constituents of slow-reacting substance of anaphylaxis (SRS-A). LTE4 is considerably less active (8 to 12-fold) than LTC4 in the biological activities characteristic of cysteinyl leukotrienes. Unlike LTC4 and LTD4, LTE4 accumulates in both plasma and urine. Therefore, urinary excretion of LTE4 is often used as an indicator of asthma. In humans, basal levels of LTE4 range from 1-100 pg/mg creatinine. In asthmatic patients, urinary LTE4 levels increase to 80-1,000 pg/mg creatinine.
