Follicular GCs were obtained through intraperitoneal injections of 10, 5, 2, and 2 IU FSH at 12 h intervals. For the enrichment of Kla-modified peptides, the tryptic peptides were solubilized in NETN buffer (1 mM EDTA, 50 mM Tris–HCl, 100 mM NaCl, 0.5% NP-40, pH 8.0) and then incubated with prewashed beads (PTM Bio) at 4 °C for 12 h. Elution of the bound peptides was achieved using trifluoroacetic acid (0.1%). The eluted peptides were subsequently vacuum-dried and subjected to desalting using C18 ZipTips (Millipore) prior to LC‒MS/MS analysis.