Pronunciation: (throm"bu-plas'tin),[key] —n. 1. Biochem.a lipoprotein in the blood that converts prothrombin to thrombin.
2. Pharm.a commercial form of this substance, obtained from the brains of cattle, used chiefly as a local hemostatic and as a laboratory reagent in blood prothrombin tests. Also called throm•bo•ki•nasePronunciation: (throm"bō-kī'nās, -kin'ās).[key]