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. Author manuscript; available in PMC: 2019 Jun 19.
Published in final edited form as: Biochemistry. 2018 Mar 28;57(24):3359–3363. doi: 10.1021/acs.biochem.8b00204

Figure 1.

Figure 1

Irreversible inactivation of human TG2 by cystamine. (A) Residual enzyme activity after incubation of TG2 with cystamine (100 μM) for the indicated times, followed by removal of cystamine by size exclusion. (B) Comparative time-dependent inactivation of TG2 by cystamine, cystine, and GSSG. Values are the mean of three technical replicates, and error bars show the standard deviation. Solid lines are fits to a single-exponential decay equation for irreversible enzyme inhibition, as described in the text. (C) Determination of the pseudo-first-order rate constant (k′) as a function of cystamine concentration. Error bars represent the standard error of the fit of the experimental data to the exponential decay equation (eq 1) obtained for the given cystamine concentration (panel B and Figure S1). Data in all panels were collected at a TG2 concentration of 10 μM in 50 mM Tris and 1 mM EDTA at pH 7.6 and 22 °C.