Merck, P5318-25MG, Pepstatin A

Pepstatin A is a naturally occurring chemotactic peptide and inhibitor of aspartic proteases that was initially isolated from culture filtrates of various Actinomycetes species, with the initial name simply of “pepstatin”. This name was later modified to “pepstatin A” to distinguish the original pepstatin from later derivatives. Pepstatin A notably contains the unusual amino acid 4-amino-hydroxy-6-methylheptanoic acid (AHMHA), which is known also as statine. The amino acid sequence of pepstatin A is N-Isovaleryl-L-Valyl-L-Valyl-AHMHA-L-Alanyl-AHMHA.