| Popis: |
Kinetic analysis of methyl group transfer from S-adenosyl-L-methionine (SAM) to the 5"-GGATCC recognition site catalyzed by the DNA-[N4-cytosine]-methyltransferase from Bacillus amyloliquefaciens [EC 2.1.1.113] has shown that the dependence of the rate of methylation of the 20-meric substrate duplex on SAM and DNA concentration are normally hyperbolic, and the maximal rate is attained upon enzyme saturation with both substrates. No substrate inhibition is observed even at concentrations many times higher than the KM values (0.107 μM for DNA and 1.45 μM for SAM), which means that no nonreactive enzyme–substrate complexes are formed during the reaction. The overall pattern of product inhibition corresponds to an ordered steady-state mechanism following the sequence SAM↓DNA↓metDNA ↑SAH↑ (S-adenosyl-L-homocysteine). However, more detailed numerical analysis of the aggregate experimental data admits an alternative order of substrate binding, DNA ↓ SAM ↓}, though this route is an order of magnitude slower. |
Full text from SpringerLink