Glutathione S-transferase omega 1 (GstO1) is closely associatedwith various human diseases, including obesity and diabetes,but its functional mechanism is not fully understood. In thepresent study, we found that the GstO1-specific inhibitor C1-27effectively suppressed the adipocyte differentiation of 3T3-L1preadipocytes. GstO1 expression was immediately upregulatedupon the induction of adipocyte differentiation, and barely alteredby C1-27. However, C1-27 significantly decreased the stabilityof GstO1. Moreover, GstO1 catalyzed the deglutathionylationof cellular proteins during the early phase of adipocytedifferentiation, and C1-27 inhibited this activity. These resultsdemonstrate that GstO1 is involved in adipocyte differentiationby catalyzing the deglutathionylation of proteins critical for theearly phase of adipocyte differentiation.