Alpha-pyridine nucleotides as substrates for a plasmid-specified dihydrofolate reductase.
Proc Natl Acad Sci U S A
; 80(15): 4619-23, 1983 Aug.
Article
en En
| MEDLINE
| ID: mdl-6410395
The alpha epimers of pyridine nucleotides are almost totally inactive as reductants in dehydrogenase reactions. In contrast, the R plasmid R67-specified dihydrofolate reductase (5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) isolated from trimethoprim-resistant Escherichia coli utilized alpha-NADPH and alpha-NADH in addition to the "normal" beta-epimers. The enzymes from bacterial and mammalian sources used only beta-NADPH and beta-NADH. THe Km value for alpha-NADPH (16 microM) was 4-fold greater than that for beta-NADPH (4 microM), while the maximal velocity of the alpha-NADPH-catalyzed reaction was 70% of that seen with the beta-NADPH. beta-NADP+ and alpha-NADP+ were competitive inhibitors of the R67 enzyme. Pyridine nucleotide analogues such as deamino- and acetyl-NADPH were used readily by bacterial, plasmid, and mammalian enzymes, whereas thio-NADPH was used only by the plasmid enzyme. These data suggest that the enzyme from R plasmid R67 possesses a pyridine nucleotide binding site different from that of other dihydrofolate reductases and dehydrogenases.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Plásmidos
/
Tetrahidrofolato Deshidrogenasa
/
Bacterias
/
Hígado
/
NAD
/
NADP
Límite:
Animals
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
1983
Tipo del documento:
Article
Pais de publicación:
Estados Unidos