29 For the serine protease family, 11 structural entries from the thrombin subfamily (1ai8, 1avg, 1hao, 1mkx, 1ucy, 2hpp, 3hk3, 3k65, 3nxp, 3pma, 3qlp), 15 structural entries from the trypsin family (... aoj, 1aks, 1an1, 1fxy, 1hj8, 1jrs, 1pq7, 2a31, 2eek, 2f91, 2ra3, 3beu, 3fp7, 3mi4, 3p95) and 4 structural entries from the plasminogen activator (1a5h, 1a5i, 1bqy, 1rtf) subfamily were used for the construction of the structural alignment.