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Abstract
SUMMARY: Bacillus megaterium 216 was induced with d-galactose to form galactokinase (EC 2.7.1.6) in amounts comparable with those induced in Escherichia coli K12. When compared with the basal level, the increase was 20 times greater than in E. coli.
The greater the concentration of d-galactose, the greater the production of galactokinase in both protoplasts and whole bacteria. In each case the maximum amount of enzyme was induced by 5 mm d-galactose. d-Fucose, a gratuitous inducer, produced approximately half the specific activity of enzyme in protoplasts as d-galactose at any particular concentration. The yield of enzyme in the presence of an optimal concentration of d-galactose was increased when the medium was fortified with low concentrations of casein hydrolysate. The specific activities of galactokinase induced in protoplasts and in whole bacteria were respectively 148 % and 37 % greater in the presence of 0·01 % casein hydrolysate.
The maximum specific activity of galactokinase achieved after induction of protoplasts for 60 min. was 3·7 units/mg. protein compared with 12·5 units/ mg. protein in whole bacteria. However, over the first 15 min. after the addition of inducer the same specific activity of galactokinase was achieved in protoplasts as in whole bacteria.
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