Tyrosine phenol lyase catalyzes the reversible conversion of tyrosine to phenol,

Question

Tyrosine phenol lyase catalyzes the reversible conversion of tyrosine to phenol, pyruvate and ammonium. The enzyme uses pyridoxal 5-phosphate (PLP) as a cofactor. The enzyme catalyzes similar reactions as well, for example the reversible conversion of L-dopa (3,4 dihydroxy L-phenylalanine) to catechol pyruvate and ammonium An assay for the activity of this enzyme involves incubating excess phenol, pyruvate and ammonium with the enzyme sample for a measured length of time. After the termination of the reaction, the L tyrosine present in the sample is quantified by liquid chromatography The following solutions are mixed 500 100 100 100 1.3 MNH4C100M Na+EDTA pH adjusted to 8.5 80 mM Na2SO3 (a reducing agent to stabilize the reaction) 800 mM Pyruvate 1.0mM PLP 500 mM Phenol 100 . At t-0, you add 100 L of an enzyme solution known to have a protein concentration of 8.5 g/mL. After 70 minutes, you add 100 L trichloroacetic acid which terminates the reaction Using the HPLC, you find that the concentration of L-tyrosine in this final solution is 2.3 mM ) What is the activity of the oniginal enzyme solution (in IUmL)? i) What is the specific activity of the oniginal enzyme sobution (in IUmg protein)?

Explanation / Answer

Tyrosine phenol lyase catalyzes the reversible conversion of tyrosine to phenol,

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