ssK36 is a super-substrate peptide derived from the histone methyltransferase (SET) domain protein 2 (SETD2). This peptide was specifically designed for SETD2, a unique PKMT responsible for methylating the 36th lysine residue on histone H3 (H3K36) in human cells, resulting in H3K36me3. Remarkably, ssK36 undergoes methylation by SETD2 at a rate over 100 times faster than the natural substrate H3K36. ssK36 serves as a valuable tool for investigating the catalytic mechanisms of PKMTs, particularly regarding substrate specificity and catalytic efficiency.