Caspase-6 is an endopeptidase[1] involved in apoptosis. In terms of its catalytic function, it is a part of the cysteine-aspartate family [2]. Before Caspase-6 becomes functional and active, the enzyme exists as a , also known as a zymogen [3]. In solution, two zymogens are associated together, forming a homodimer. Zymogen activation, the process by which Caspase-6 becomes active, is largely conserved across the caspase family.
However, Caspase-6 is unique in that it becomes active through self-cleavage rather than cleavage by a separate enzyme. Each zymogen of the unprocessed enzyme contains a consisting of two helices and subunit consisting of three helices, a , as well as an intersubunit linker. The helices surround a beta sheet core. In order to become active, the intersubunit linker is bound to the active site of Caspase-6, where it is then cleaved. After cleavage, the four processed subunits, two originating from each zymogen, remain closely associated together through intermolecular forces, forming a dimer of dimers.
