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Sulfite Oxidase

Structure of the molybdenum centre of sulfite oxidase enzymes

Structure

The pyranopterin ligand which coordinates the molybdenum centre via the enedithiolate

The molybdenum centre has a square pyramidal geometry and is distinguished from the xanthine oxidase family by the orientation of the oxo group facing downwards rather than up.

Vertebrates

Structure of sulfite oxidase isolated from chicken liver

X-ray crystallography has confirmed the structure of sulfite oxidase enzymes from chickens^[1]. It is a homodimer with two N-terminal heme groups that are very similar in structure and sequence to that of cytochrome b₅. Each domain is connected via a 12-15 long amino acid chain to the molybdenum centre.

Molybdenum active site of sulfite oxidase from chicken liver

Heme site in sulfite oxidase from chicken liver

Plants

X-ray crystallography has confirmed the structure of sulfite oxidase enzymes from A. thaliana^[1]. This enzyme is similar in structure to that of vertebrates but does not contain the heme domain, making the molybdenum centre the only redox active site.

Mechanism

Electrons are passed one at a time from the molybdenum to the heme group which reacts with cytochrome c to reoxidize the enzyme. The electrons from this reaction enter the electron transport chain (ETC).

Reductive half reaction

This reaction is generally the rate limiting reaction. Upon reaction of the enzyme with sulfite, it is reduced by 2 electrons. The negative potential seen with re-reduction of the enzyme shows the oxidized state is favoured.

Oxidative half reaction

Among the Mo enzyme classes, sulfite oxidase is the most easily oxidized. Although under low pH conditions the oxidative reaction become partially rate limiting.

Structure of sulfite oxidase isolated from A. thaliana

Active site in sulfite oxidase from A. thaliana

^ ^a ^b Hille, Russ; Nishino, Takeshi; Bittner, Florian (2011-05). "Molybdenum enzymes in higher organisms". Coordination Chemistry Reviews. 255 (9–10): 1179–1205. doi:10.1016/j.ccr.2010.11.034. {{cite journal}}: Check date values in: |date= (help)

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Week3 Tasks - Info for Methyl Oleate

Properties of Methyl Oleate

Molecular formula: C₁₉H₃₆O₂
Molar mass: 296.49 g/mol
Melting point: -20 °C
Boiling point: 350 °C
Solubility in water: insoluble

Methyl Oleate

Methyl Oleate

Internal link: Oleic acid

External link: Fischer Scientific - Methyl Oleate [1]

Energy Transduction in Nitrogenase ^[1]

Biosynthesis of Nitrogenase Metalloclusters ^[2]

Nitrogenase assembly ^[3]

^ Seefeldt, Lance C.; Hoffman, Brian M.; Peters, John W.; Raugei, Simone; Beratan, David N.; Antony, Edwin; Dean, Dennis R. (2018-08-10). "Energy Transduction in Nitrogenase". Accounts of Chemical Research. 51 (9): 2179–2186. doi:10.1021/acs.accounts.8b00112. ISSN 0001-4842.
^ Ribbe, Markus W.; Hu, Yilin; Hodgson, Keith O.; Hedman, Britt (2013-12-13). "Biosynthesis of Nitrogenase Metalloclusters". Chemical Reviews. 114 (8): 4063–4080. doi:10.1021/cr400463x. ISSN 0009-2665.
^ Hu, Yilin; Ribbe, Markus W. (2013-08). "Nitrogenase assembly". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1827 (8–9): 1112–1122. doi:10.1016/j.bbabio.2012.12.001. ISSN 0005-2728. {{cite journal}}: Check date values in: |date= (help)

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Critique of Carbonic Anhydrase Mechanism Figure

The mechanism does not look professionally drawn. Not all bond lengths are equal or in the right orientation. The arrows are not a good size and specifically the arrow showing water being added is not properly drawn.

Table of Properties of Methyl Oleate
Molecular formula	C₁₉H₃₆O₂
Molar mass	296.49 g/mol
Solubility in water	insoluble

$x_{1}=\left({\frac {y}{2}}\right)^{2}$

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[:0-1] Hille, Russ; Nishino, Takeshi; Bittner, Florian (2011-05). "Molybdenum enzymes in higher organisms". Coordination Chemistry Reviews. 255 (9–10): 1179–1205. doi:10.1016/j.ccr.2010.11.034. {{cite journal}}: Check date values in: |date= (help)

[2] Seefeldt, Lance C.; Hoffman, Brian M.; Peters, John W.; Raugei, Simone; Beratan, David N.; Antony, Edwin; Dean, Dennis R. (2018-08-10). "Energy Transduction in Nitrogenase". Accounts of Chemical Research. 51 (9): 2179–2186. doi:10.1021/acs.accounts.8b00112. ISSN 0001-4842.

[3] Ribbe, Markus W.; Hu, Yilin; Hodgson, Keith O.; Hedman, Britt (2013-12-13). "Biosynthesis of Nitrogenase Metalloclusters". Chemical Reviews. 114 (8): 4063–4080. doi:10.1021/cr400463x. ISSN 0009-2665.

[4] Hu, Yilin; Ribbe, Markus W. (2013-08). "Nitrogenase assembly". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1827 (8–9): 1112–1122. doi:10.1016/j.bbabio.2012.12.001. ISSN 0005-2728. {{cite journal}}: Check date values in: |date= (help)

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