Figure 1. Biochemical and Cellular HDAC inhibition by 4b.

(A) % inhibition of human recombinant Class I enzymes HDAC1 (red), HDAC2 (green), HDAC3 (black) and HDAC8 (blue) by 4b. (B) No inhibition of ClassIIa/b enzymes by 4b; HDAC 4(green), HDAC5 (red), HDAC7 (purple), HDAC9 (orange), HDAC6 (brown). (C) Time-dependence of human recombinant HDAC3 inhibition by varying preincubation time of 4b with enzyme (as shown). (D) Cellular inhibition of endogenous Class I HDACs/HDAC6 using Boc_Lys_Ac (black traces) or Class IIa/HDAC8 HDACs using Boc_Lys_TFA substrate (red traces) by 4b (closed circles) or reference compounds SAHA and Compound 26. (E) Time- dependence of cellular Class I HDAC inhibition by varying preincubation of 4b with cells (as shown). (F) Plot of IC₅₀ values versus compound-cell preincubation time for SAHA (green) and 4b (black).