Final answer:
XIAP serves as an inhibitor of caspases by binding to and inhibiting their activity, thus playing a key role in the regulation of apoptosis and maintaining cellular homeostasis.
Step-by-step explanation:
XIAP, which stands for X-linked inhibitor of apoptosis protein, functions as an inhibitor of caspases, which are proteolytic enzymes playing a crucial role in the process of apoptosis, or programmed cell death. XIAP impedes the apoptotic process by binding to and inhibiting the activity of certain caspases, including caspase-3, caspase-7, and caspase-9. This inhibition is an example of how cells can regulate apoptosis and ensure that it occurs appropriately during development and in response to cellular stress or damage. Inhibitors like XIAP are essential for maintaining the balance between cell survival and cell death, which is a critical aspect of cellular and tissue homeostasis.