1. What is the keat of this enzyme? 2. At which concentration of the substrate this enzyme reaches initial reaction velocity (Vo) of 500 nMis (assuming (otal is the same 10 nMy? 3. What is the maximum reaction velocity (Vmax) of the reaction catalyzed by this enzyme at (Etotail4 nM? of the items from the answer list should NOT be used.

1. ( . tion can be represented by the so-called Michaelis equation ) The velocity of an enzyme catalyzed reac- Vmax [S] Vo = Km Vo = max kcat [Eo] [So] (Км + [Sol) V max where [So] is the initial substrate concentration, [Eo] is the total enzyme concentration, kcat is the cataly- tic rate constant or turnover number, and KM repre- sents the Michaelis constant. The graph on the right illustrates the dependence of the velocity of the reaction as a function of substrate concentration. Ex- Km [S] (mm) plain why the maximal velocity can be represented by the expression Vmax = Kcat [Eo] at very high substrate concentrations. Vo (µm/min)

8.Choose the False statement about enzyme binding sites Binding at an allosteric site ca affect binding and catalysis at the Ortho steric site. In addition to ortho steric sites , some enzymes have other sites where catalysis can be conducted. They are called , allosteric sites, from “allo,” the other. In principle, allosteric ligands can have structures that do not resemble those of substrates. Ligand binding at an allosteric site can cause a conformational change of an enzyme. Enzyme can be inhibited by an allosteric ligand that does not complete with substrate.

1. Consider the following parameters related to an enzyme that follows Michaelis-Menten kinetics for the reaction: k(1) k(2) S ----> ES ----> P k(-1)

1. The concentration of substrate X is high. What happens to the rate of the enzyme-catalyzed reaction if the concentration of substrate X is reduced? Explain. 2. An enzyme has an optimum pH of 7.2. What is most likely to happen to the activity of the enzyme if the pH drops to 6.2? Explain

Part 1: Assess the following partial results section below by editing it for brevity by omitting any unnecessary parts (1 point), explain why you decided to remove certain sections (1 point): To evaluate inhibitory effects of the selected molecules, 10mM stock solutions of each molecule were prepared in DMSO. A reaction mixture (200μl) was prepared with the same formula optimized for the enzyme activity assay (0.1 M Tris-HCl ph 8, 0.1 M KCI, 25 mM NaCl, 0.25 mM ATP, and two units of inorganic yeast pyrophosphatase) with 10 µM of the sample molecule. The reaction mixture was incubated for 20 minutes at ambient temperature. Enzymatic reaction was triggered by addition of the substrate B (0.2 mM) and the absorbance of the product was monitored at 290 nm for 10 minutes. Six out of 15 sample molecules showed appreciable inhibition at 10 μM (Figure 5). Three of the molecules, A3, A6, and A7 exhibited more than 50% inhibition of the enzyme activity and were further diluted to find the minimal…