Any of a group of proteins, found in all groups of organisms except fungi, that are characterized by irreversibly inhibiting serine proteases (i.e. proteases with a serine residue at the active site). Serpins, which can occur both inside and outside cells, are involved in a wide range of metabolic processes, including regulation of complement activation, blood coagulation, tumour suppression, inflammation, and blood vessel formation (angiogenesis). The most abundant serpin in human plasma in α1-antitrypsin, which inhibits trypsin and, most significantly, elastase released by leucocytes. Some proteins lacking inhibitory activity are also classified as serpins, including angiotensinogen, the precursor of angiotensin.
Subjects: Science and Mathematics — Medicine and Health.