Replacement of isoleucine-397 by threonine in the clotting proteinase factor IXa (Los Angeles and Long Beach variants) affects macromolecular catalysis but not L-tosylarginine methyl ester hydrolysis. Lack of correlation between ox brain prothrombin time and the mutation site of variant proteins - Spitzer, S G; Warn-Cramer, B J; Kasper, C K; Bajaj, S P (Biochem J, 1990)