In rats, four types of kininogens are produced, two of which are classical high and low molecular weight kininogens and two of which are low molecular weight-like kininogens, designated T-kininogen 1 and T-kininogen 2. T-kininogen 1 and T-kininogen 2 are 430 amino acid secreted rat proteins that each contain three cystatin domains and have nearly identical functions. Existing in plasma, both T-kininogen 1 and T-kininogen 2 are glycoproteins that act as thiol protease inhibitors and also play a role in blood coagulation, specifically by helping to optimally position blood coagulation factors. Additionally, T-kininogen 1 and T-kininogen 2 act as precursors of the active peptide Bradykinin and, as such, effect vascular permeability, hypotension and smooth muscle contraction.