Plant hormones are molecules with vital regulatory functions in growth, development, and defense signaling. Major components of biotic and abiotic stress responses are reliant on plant hormone signaling. The plant hormone salicylic acid (SA) has a crucial role in mounting and orchestrating plant defense responses. Thimet oligopeptidase 1 (TOP1) and thimet oligopeptidase 2 (TOP2), are two metallopeptidases capable of interacting with SA. The characterization of TOP function has elucidated roles in plant immunity and oxidative stress responses. We investigated multiple aspects of TOP regulation. We have determined that TOPs form redox-sensitive oligomers. Additionally, our findings suggest that the cellular redox-regulator, glutathione, regulates TOP oligomerization. Furthermore, the activities of TOPs are modulated by thiols. In addition, we examined the expression profile of SA-binding proteins in plant immune-related conditions. We identified five genes encoding putative SABPs that are co-expressed and upregulated during biotic stress responses and SA-regulated processes.