Kinetics and template-dependency of ribonucleic acid synthesis by bacterial ribonucleic acid polymerase.

The rate of RNA synthesis catalysed by DNA-dependent RNA polymerase shows a Michealis-Menten-type saturation curve with increasing template concentration. However, the apparent Km is proportional to enzyme concentration, indicating that the reaction does not obey a simple kinetic scheme. The action of inhibitors also indicates a more complex interaction between the enzyme and the DNA template; many inhibitors of RNA synthesis either decrease Vmax. without affecting Km, or increase Km without affecting Vmax. All of these observations can be accounted for quantitatively by a reaction pathway in which the non-specific binding sites of the viral DNA template inhibit competitively the binding of the enzyme to the initiation sites. In terms of this pathway the two classes of inhibitors of RNA synthesis must then act predominantly either on the rate of elongation or on the availability of the binding sites respectively.