Lipoic acid is often found near the active sites of enzymes, usually bound to the

Chapter 24, Problem 24-40

(choose chapter or problem)

Lipoic acid is often found near the active sites of enzymes, usually bound to the peptide by a long, flexible amide linkage with a lysine residue. COOH S lipoic acid S S S C O N H CH C O NH bound to lysine residue (a) Is lipoic acid a mild oxidizing agent or a mild reducing agent? Draw it in both its oxidized and reduced forms. (b) Show how lipoic acid might react with two Cys residues to form a disulfide bridge. (c) Give a balanced equation for the hypothetical oxidation or reduction, as you predicted in part (a), of an aldehyde by lipoic acid. R C O H + COOH S S H2O