Kallikreins (tissue and plasma kallikrein) are serine proteases that liberate kinins (BK and KD) from the kininogens. Prekallikrein is the precursor of plasma kallikrein. It can only activate kinins after being activated itself by factor XII or other stimuli.

There are 15 kallikreins (KLK1-KLK15).

See also

• Kinin-kallikrein system
• Kinin