Question

Trypsin is a protein that reacts with the substrate, dihydrogen dioxide, and yields the values of Km and Vmax. Trypsin 6 (a variation of Typsin) also reacts with the substrate, dihydrogen dioxide, but results in double the Km and Vmax values.

1. Sketch the Lineweaver-Burke graph for Trypsin and Trypsin 6

2. Explain how and why these graphs differ

Hint: Consider substrate concentration

Answer 1

Take an example, 4 is bigger than 2 but 1/4 that is 0.25 is lesser than ½ that is 0.5. Same thing is happened in this case.

Trypsin and trypsin 6 both the enzyme have the same substrate but their Km and Vmax value is different. So why this is happening, the main reason behind this different value is the substrate concentration. From the definition of Km, we know that it is the substrate concentration at which half or 50% of the reaction is completed. In other way we can say that, the substrate binding site of the enzyme is half occupied by the substrate. And, Vmax is the point at which the enzyme is fully occupied by the substrate or we can say the enzyme is saturated with the substrate. The enzyme-substrate reaction reaches its saturation point.

So, the value of Km is directly proportional to the substrate concentration and also depends on the affinity of the enzyme for the substrate. The higher the affinity of the enzyme, the lower the amount of substrate will be required to complete the 50% of the reaction. So, the value of Km will be less. And also the amount of substrate required to attain the Vmax will be higher for those enzyme which has a lower substrate affinity.

This is the reason for having a higher values of Km and Vmax for trypsin 6 and lower for trypsin.