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. Author manuscript; available in PMC: 2017 Feb 19.
Published in final edited form as: ACS Chem Biol. 2015 Dec 14;11(2):415–424. doi: 10.1021/acschembio.5b00731

Table 3.

20S proteasome inhibitory activities of thiostrepton Ala2 analogues

IC50 (μM)
Compound Trypsin-
like		 Chymotrypsin-
like		 Caspase-
like
Thiostrepton A 0.95 ± 0.15 1.0 ± 0.1 0.59 ± 0.06
Ala2Dha 0.71 ± 0.07 0.99 ± 0.01 0.51 ± 0.03
Ala2Dhb 1.3 ± 0.2 3.1 ± 0.3 0.92 ± 0.06
Ala2Gly 1.2 ± 0.1 0.76 ± 0.12 0.37 ± 0.04
Ala2Ile-ΔIle1 2.1 ± 0.4 6.3 ± 0.4 1.6 ± 0.3
Ala2Met 0.09 ± 0.01 0.62 ± 0.01 0.14 ± 0.01
Ala2Phe 0.18 ± 0.02 0.96 ± 0.03 0.46 ± 0.04
Ala2Tyr 0.34 ± 0.03 >0.92a 0.58 ± 0.09
Ala2Val-ΔIle1 0.84 ± 0.04 3.9 ± 0.2 1.2 ± 0.04
Bortezomib 1.6 ± 0.2 0.005 ± 0.001 0.049 ± 0.003
a

IC50 not determined due to solubility limitation.