“Kinetic analysis of equivalent amounts of wild type … proteins showed that mutagenesis of active site Serines resulted in modest … Km values for corticosterone from 325 nM for 11 beta HSD1 to 512 nM-588 nM for … (YAASK), S2 (YSAGK) and S3 (YAAGK) mutants in homogenates of transfected CHOP cells.”