problem_set_5_KEY_v2

problem_set_5_KEY_v2 - 7.05 Problem Set 5 Spring 2008 1....

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Unformatted text preview: 7.05 Problem Set 5 Spring 2008 1. What is the function of the following types of enzymes? a. Isomerase catalyzes the conversion of one isomer to another b. Mutase catalyzes the transfer of a phosphate group from one position to another within the same molecule c. Epimerase catalyzes the inversion of the configuration of the OH group on a chiral carbon d. Enolase catalyzes the conversion of C=C groups to alcohol without changing the oxidation state e. Aldolase catalyzes an aldol condensation reaction f. Dehydrogenase catalyzes the removal of hydrogens by oxidation g. Kinase catalyzes the transfer of a phosphate group from a donor (usually ATP) to an acceptor h. Phosphorylase catalyzes the addition of a phosphate group from an inorganic phosphate to an acceptor i. Phosphatase catalyzes the removal of a phosphate group 2. The systematic name of melezitose is α‐D‐glucopyranosyl‐(1 3)‐β‐D‐fructofuranosyl‐(2 1)‐α‐D‐ glucopyranoside. Draw its molecular formula. Is it a reducing sugar? OH OH O HO OH OH HO O O OH HO OH OH O O OH Melezitose is not a reducing sugar because it has no potentially free aldehyde group. 3. Exam 3 2005 Question 1 Assume that liver tissue can synthesize enzymatically the tetrasaccharide shown below from free fructose. Give the formal name of the tetrasaccharide and show how liver tissue could enzymatically convert four fructose units to the phosphate esters of the monosaccharide units needed for the formation of the tetrasaccharide. α‐D‐galactopyranosyl‐(1 4)‐β‐D‐mannopyranosyl‐(1 6)‐α‐D‐glucopyranosyl‐(1 2)‐β‐D‐fructofuranoside 4. 3‐phosphoglycerate is labeled uniformly with 14C as well as 32P. What is the radioisotope distribution of the 2‐phosphoglycerate that is formed on addition of phosphoglycerate mutase? Trace the fate of the 32 P. The 2‐phosphoglycerate produced contains all the 14C label. The 32P label ends up being attached to the His residue in the active site of phosphoglycerate mutase, and no 32P is present in the 2‐ phosphoglycerate after the first round of enzyme action. The fate of the 32P is as follows, where the red phosphate group represents the labeled group: 5. Fill in the following table, indicating the effect of high concentrations of the following compounds, as well as the specific enzymes the compounds act on to activate or inhibit. Compound Effect on glycolysis Activates Inhibits Fructose‐2,6‐bisphosphate Stimulates phosphofructokinase fructose‐1,6‐bisphosphate Fructose‐1,6‐bisphosphate Stimulates pyruvate kinase ATP Inhibits phosphofructokinase pyrvate kinase AMP Stimulates pyruvate kinase fructose‐1,6‐bisphosphate PKA Stimulates phosphorylase glycogen synthase 6. Exam 3 2006 Question 3 Show how compounds A and B (shown below) could be converted to compound C in the presence of a single enzyme of the type discussed in class. Use structural formulas and include the chemical mechanisms and any proposed enzyme‐bound intermediates. 7. Exam 3 2004 Question 3 Show how mannose could be used to provide all the carbons of lactose. Please give the enzymatic pathway and indicate by name the enzymes and intermediates involved in the proposed reactions. Use only enzymes that were mentioned in class. No need to provide formulas unless, by doing so, it helps to provide answers. ...
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