Serpins (serine protease inhibitors) are a superfamily of proteins whose physiologi cal action
is primarily targeted to inhibiting serine proteases. There are instances where serpins are not
inhibitors (and can carry steroid hormones for instance) yet key structural and functional
elements found in all serpins are maintained in these 'non-inhibitor' ser pins. Many serpins
have well-described biological properties which influence pathophysi ological events
including: antithrombin (historically called antithrombin III) ai-protease inhibitor
(historically called ai-antitrypsin) and plasminogen activator inhibitor-I just to mention a
few. A deficiency or defect in antithrombin leads to venous thromboembolic disease while a
deficiency or defect in ai-protease inhibitor is associated with chronic obstructive pulmonary
emphysema. In contrast it has been suggested that increased levels of plasminogen activator
inhibitor-l may be a predisposition to myocardial infarction. The list goes on for each of our
own favorite serpin. The biological roles found for serpins are key participants in almost
every physiological event. In other words serine proteases are needed for many events in
biology and the role of serpins to down regulate these pro teases is essential. Thus just
using these three examples above for serpins and their patho physiological roles reminds us
that the medical costs to control such events is significant worldwide.
