Inhibition of this enzyme has been associated with

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Inhibition of this enzyme has been associated with neutral tube defects and heart disease. It is also a potential chemotherapeutic target. TRANSITION METALS Methionine synthase requires vitamin B 12 and zinc. CH 3 Zn +2 site Methylcobalamin (methylB 12 ) zinc site The corrin ring is a ______dentate ligand d-count? Chelate effect? color?
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: 36.2 OXIDATION/REDUCTION Think about the reactions of methionine synthase: REVIEW Vitamin B 12 is reduced by a protein called flavodoxin. for vitamin B 12 is -0.526 V for flavodoxin is -0.230 V Which is a better reducing agent? E °(cell) = E °(reduction) - E ° (oxidation) = (vitamin B 12 ) - (flavodoxin) = -0.526 V -(-0.230 V) = -0.296 V Is the reduction of vitamin B 12 by flavodoxin spontaneous? = -n E ° = -(1)(96485 Cmol -1 )(-0.296 V) = +28.6 kJ/mol S -adenosylmethionine provides the energy to drive the reaction. The G° for the cleavage of S- adenosylmethionine is -37.6 kJ/mol
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36.3 Cells that require energy to bring about non-spontaneous reactions are called? ACID-BASE EQUILBRIUM O O O + H 3 N CH C O - + H 3 N CH C O - + H 3 N CH C O - CH 2 -H + CH 2 +CH 3 CH 2 CH 2 CH 2 CH 2 SH S - S CH 3 protonated homocysteine deprotonated homocysteine methionine At physiological pH (7.4), how much homocysteine is deprotonated? pK a for homocysteine is 10 Free homocysteine is _________________ and non-reactive at physiological pH pHs above the pK a A - A - A - A - A A - A - A - H A H A H A - A - = pH = pK a pHs below the pK a A H A A A - H H A H A H A H A H
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36.4
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