A slow, tight binding, competitive aminopeptidase (AP) inhibitor, first described as an inhibitor of AP-A (glutamyl AP; IC50 = 0.54 µg/ml) but not of AP-B (arginine AP); also inhibits AP-N (AP-M, alanyl AP; Ki = 20-200 nM), leucyl-cystinyl AP (Ki = 20-220 nM), and endoplasmic reticulum AP 1 (Ki = 41.8 µM).