Figure 4. A generic model for the competition of reactions which are catalyzed by the same enzyme.

The same substrate MeIQx is transformed into two different compounds by the same enzyme CYP1A2. The symbol α denotes the distribution coefficient of enzyme concentration spread in the two reactions (A). The enzyme UGT is involved in the catalysis of two reactions which are in competition with respect to the UGT concentration. This concentration is depicted by the distribution coefficient β (B).