The pH 6 Acetolactate‐Forming Enzyme from Aerobacter aerogenes

Crystalline pH 6 acetolactate‐forming enzyme from Aerobacter aerogenes contains 4 thiol groups per enzyme molecule, determined with 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB) in 50 mM sodium dodecyl sulfate, or acetate. In the presence of 50 mM pyruvate, propionate, as well as acetamide, 3 thiol groups are accessible for titration with DTNB. In the presence of phenylpyruvate, 2.3 thiol groups reacted. The apparent Michaelis kinetics, obtained in the presence of acetate, is not altered after 1–3 thiol groups are allowed to react with DTNB.