Next: 9. Immunochemistry Up: 8. Enzymes and Other Proteins Previous: Chymotrypsin
These are zinc metalloenzymes that oxidize alcohols to aldehydes or ketones. Zinc is bound to the sulphur atoms of Cys-46 and Cys-174 and a nitrogen atom of His-67. An ionizable water molecule occupies the fourth position on the zinc. This water is hydrogen-bonded to the hydroxyl of Ser-48. The oxygen atom of substrate is believed to bind directly to the zinc ion. The nicotinamide ring of NAD+ is bound close to the zinc. In the oxidation of alcohol two hydrogen atoms are removed - one to the 4-position of NAD+ and the other as a proton. The transfer to NAD+ is generally throught to be hydride transfer.
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