3.2.2.8 H239A dramatic increase in Km for uridine, unchanged kcat 657373 3.2.2.8 H82N small increase in Km, increase in kcat 657373 3.2.2.8 additional information mutants expressing the Arabidopsis thaliana enzyme or the homologue from Oryza sativa exhibit resistance toward toxic fluorouridine, fluorouracil, and fluoroorotic acid. Mutants with increased and decreased nucleosidase activity are delayed in germination 700741 3.2.2.8 Q227A the mutation causes an increase of kcat for uridine and inosine 696258 3.2.2.8 Q227F the mutation causes an increase of kcat for uridine and inosine 696258 3.2.2.8 Q227Y the mutation has a strong, enhancing effect on the hydrolysis of inosine, and the catalytic efficiency for the purinic substrate is increased by a factor of 7.6 696258 3.2.2.8 T223A the mutation does not improve significantly the catalytic efficiency of YeiK toward inosine 696258 3.2.2.8 T223F the mutation does not improve significantly the catalytic efficiency of YeiK toward inosine 696258 3.2.2.8 T223F/Q227Y the mutant shows a 2fold increase in catalytic efficiency toward inosine 696258 3.2.2.8 T223Y the mutation does not affect the specificity of the enzyme toward inosine or uridine 696258