The question has been answered recently by these people:
Li CY, de Veer SJ, Law RHP, Whisstock JC, Craik DJ, Swedberg JE
Characterising the Subsite Specificity of Urokinase-Type Plasminogen Activator and Tissue-Type Plasminogen Activator using a Sequence-Defined Peptide Aldehyde Library.
Chembiochem. 2018 Sep 17. doi: 10.1002/cbic.201800395. [Epub ahead of print]