Because it resembles the two physiological substrates, phosphonacetyl L - aspartate (PALA) is a strong inhibitor of ATCase. Low concentrations of this unreactive bisubstrate analog, on the other hand, enhance reaction velocity in the presence of substrates. The reaction rate rises as PALA is added, until three molecules of PALA are attached per molecule of enzyme. This maximum velocity is 17 times higher than it would be without PALA. With the addition of three additional molecules of PALA per molecule of enzyme, the reaction rate drops to practically nil. Why does PALA activate ATCase at such low concentrations?

Because it resembles the two physiological substrates, phosphonacetyl L - aspartate (PALA) is a strong inhibitor of ATCase. Low concentrations of this unreactive bisubstrate analog, on the other hand, enhance reaction velocity in the presence of substrates. The reaction rate rises as PALA is added, until three molecules of PALA are attached per molecule of enzyme. This maximum velocity is 17 times higher than it would be without PALA. With the addition of three additional molecules of PALA per molecule of enzyme, the reaction rate drops to practically nil. Why does PALA activate ATCase at such low concentrations?

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 20P: Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy...

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