THREONINE SYNTHASE, A SYSTEM SYNTHESIZING l -THREONINE FROM l -HOMOSERINE

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Abstract
Suspensions of Escherichia coli synthesize L-threonine from L-homoserine in the presence of glucose, phosphate, and air. L-Threonine was identified chromatographically and microbiologically. D-Homoserine is not transformed. The kinetics of the reaction are complicated by the presence of threonine deaminase, but this inconvenience can be eliminated if the system is studied at pH 4.8. In general, mutants blocked between homoserine and threonine could not be shown to possess threonine synthase activity, whereas those growing on either homoserine or threonine had a normal threonine synthase activity. There are exceptions to this rule.