Role of L-Threonine Deaminase and L-Threonine 3-Dehydrogenase in the Utilization of L-Threonine by Pseudomonas aeruginosa

Department of Biochemistry, University of Hong Kong, Li Shu Fan Building, Sassoon Road, Hong Kong ABSTRACT SUMMARY: Mutants of Pseudomonas aeruginosa PAC1 which could grow on L -threonine were isolated. These mutants, like the parent strain, synthesized a biosynthetic threonine deaminase, but its apparent K m value for threonine was higher than that of the enzyme from strain PAC1. These mutants also synthesized an inducible NAD-dependent threonine dehydrogenase, which was not present in the parent strain. No threonine aldolase activity could be detected. The results suggest that the threonine deaminase with lowered affinity for L -threonine, together with L -threonine dehydrogenase, enabled these mutants to utilize L -threonine as the sole source of carbon for growth.