The Staphylococcus aureus transpeptidase Sortase A (SrtA) anchors virulence and colonization-associated surface proteins to the cell wall. SrtA selectively recognizes a C-terminal LPXTG motif. SrtA readily reacts with its native substrate Abz-LPETG-Dap(DNP)-NH2, cleaving it and catalyzing the formation of an amide bond between the carboxyl group of threonine and the amino group of cell-wall crossbridges.

Human proinsulin, the single-chain peptide precursor of insulin, consists of the insulin A and B chains connected by the 31 amino acid C-peptide. Cleavage of proinsulin by proteolytic enzymes produces insulin and free C-peptide.

4-Methyl-2-pentanone is an organic solvent. It is occasionally found as a volatile component of urine. It in urine is considered a biological marker of occupational exposure to this solvent.