Automatic fluorescence titrations and their interpretation.
Explore the source record for details and available documents.
Adenosine Triphosphate↗
Biomedical subjects
G R Penzer
Publications and source records attributed to G R Penzer.
The effects of spermine and Mg2+ on the catalytic mechanism of isoleucine: tRNA ligase.
Isoleucyl-tRNA formation catalysed by isoleucine: tRNA ligase is stimulated by both Mg2+ and spermine in the pH-range 7.0 to 8.0 at 310 K. At low [Mg2+] the acceleration caused by both cations together exceeds the sum of their individual effects. 2. The spermine-stimulated reaction has a steeper temperature-dependence than reaction in the presence of Mg2+. Two phases in the kinetics of isoleucyl-tRNA formation are detected in the presence of Mg2+ plus or minus spermine, but only a single step is observed in the presence of spermine alone. Thus the rate-limiting steps under normal assay conditions are different for the two cations. 3. Enzyme-bound isoleucyl-AMP can be formed in the absence of Mg-2+ and plus or minus spermine. 4. It is concluded that there is no evidence for cation-dependent differences in the reaction mechanism of isoleucine: tRNA ligase, though there are certainly differences in the relative rates of some of the individual steps.
Enzyme Activation↗