Type 4

Your data show that kcat decreases as hyperbola and  1/kcat increases as hyperbola when the  concentration of modifier increases, namely

This property is shared by five basic modifier mechanisms. Two of them (left and right in the first row below) can be identified just by examining the dependence of Km on modifier concentration, [X].

For the subgroup ‘Km decreases as hyperbola’ (the choice in the middle), discrimination is made by further examining how kcat/Km varies with [X]. Click the appropriate statement to unravel the mechanism.

Km increases as hyperbola

The sought mechanism is:

Hyperbolic mixed, predominantly specific inhibition, HMx(Sp>Ca)I

Examples of HMx(Sp>Ca)I

Km decreases as hyperbola

Three mechanisms share this property and can be distinguished from the dependencies of kcat/Km on modifier concentration.

Km is independent of modifier concentration

The sought mechanism is:

Hyperbolic mixed, balanced inhibition, HMx(Sp=Ca)I

Examples of HMx(Sp=Ca)I

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