A Newborn Screening Test for Galactosemia Is Positive in Your

A newborn screening test for galactosemia is positive in your patient. Genetic studies demonstrate the infant harbors a particular mutation in the GALT gene that impairs the activity of galactose-1-phosphate uridyl transferase. The impaired enzyme cannot convert galactose 1-phosphate and UDP-glucose to UDP-galactose and glucose 1-phosphate. Galactose 1-phosphate accumulates and affects the activity of UTP-dependent glucose-1-phosphate pyrophosphorylase (UGP) . Which of the following actions by galactose 1-phosphate proves that it
Is a competitive inhibitor of UGP?

A) decreases the apparent K_m for glucose 1-phosphate
B) decreases both the V_max and the apparent Km for glucose 1-phosphate
C) decreases the V_max for glucose 1-phosphate
D) increases the apparentKmfor glucose 1-phosphate
E) increases the V_max for glucose 1-phosphate