Profiling Cystathionine β/γ-Lyase in Complex Biosamples Using Novel Activatable Fluorogens

Cystathionine lyase, the key enzyme in transsulfuration and reverse transsulfuration pathways, is involved in a wide array of physiological and pathophysiological processes in both mammals and nonmammals. Though the biological significance of the hydrogen sulfide/cystathionine lyase system in disease states is extensively discussed, the absence of molecular methods for direct monitoring of cystathionine lyase in complex biosamples renders the result unreliable and perplexing. Here, we present the first attempt at designing and developing effective activatable fluorescent probes for cystathionine lyase based on the naphthylamide scaffold. CBLP and CSEP were designed based on the catalytic preference of cystathionine β-lyase (CBL) and cystathionine γ-lyase (CSE). Briefly, incorporation of cysteine/homocysteine as the recognition moiety and a carbamate ethyl sulfide group as a self-immolated linker proved to be an effective strategy for cystathionine lyase fluorescence reporting. CBLP exhibits high selectivity and sensitivity in vitro in semiquantifying CBL levels in roots of wild-type Arabidopsis thaliana and cbl mutants (cbl knockout: SALK_014740C, overexpressed: OE-CBL). Meanwhile, CSEP successfully detected CSE levels in HCC-LM3 cells, zebrafish models, and upregulated CSE in frozen section slides from the liver tissue of cecal ligation and puncture (CLP)-induced septic rats, which was also validated by Western blotting and immunohistochemical analysis. In summary, the practical design strategy facilitates profiling of cystathionine lyase activity in biological processes. It may pave the way for the development of accurate and efficient methods for the direct estimation of cystathionine lyase.