Hyperproduction of dihydrofolate reductase in Diplococcus pneumoniae by mutation in the structural gene

摘要: Abstract A unique group of mutations (amer) in the dihydrofolate reductase (5,6,7,8-tetrahydrofolate:NADP+ oxidoreductase, EC 1.5.1.3.) structural gene Diplococcus pneumoniae determine a marked overproduction corresponding enzyme protein. Since findings with these relate to key metabolic function and may be important regulation folate coenzyme synthesis general, same multations were also examined for their effects on number related enzymic activities. Mutant wild-type cell-free extracts, addition activity, exhibited both dihydropteroate synthetic activities under conditions employed. Four coenzyme-related could demonstrated preparations. These are mediated by following enzymes, serine hydroxymethyl transferase ( l -serine: tetrahydrofolate 10-hydroxymethyl tranferase, 2.1.2.1), 5, 10-methylenetetrahydrofolate dehydrogenase (5,10-methylenetetrahydrofolate: NADP+ 1.5.1.5), 10-formyltetrahydrofolate synthetase (formate: ligase (ADP-forming), 6.3.4.3) glutamate formiminotransferase N- formimino- -glutamate: 5-formiminotransferase, 2.1.2.5). The amer current study determined 3–80-fold increases comparison wild type. However, none other folate-related altered. possible significance light previous results is discussed.