Inhibitor of ubiquitin C-terminal hydrolase-L1 (UCH-L1) activity (Ki = 0.4 μM). Causes cell death through the apoptosis pathway; increases levels of highly ubiquitinated proteins and decreases ubiquitin proteasome activity. Activity leads to dramatic alterations in synaptic protein distribution and spine morphology in vivo. Purity 98%. MW (observed): 397.64