The inflection points on each side of the curve represent the pKa of the critical R-groups in the enzyme. As with all proteins, the conformation is sensitive to temperature. As with all chemical reactions, the enzymem catalyzed reactions are temperature sensitive. This relationship is showin in Figure 2.15B on page 53. This bell-shaped curve is superficially similar in overall shape to that induced by changes in pH. Close examination of the left side of the curve shows that it is exponential.
Higher temperatures accelerate the catalytic effect.
This relationship continues up to the optimum temperature. The activity at these super-optimal temperatures falls severely to 0. In most plant cells, it is impossible to control the reaction rate by regulating the concentration of the substrate. I will try to explain that here. The Km cancels out on the left side.