Purification and general properties of δ-aminolaevulate dehydratase from Nicotiana tabacum L.

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Abstract
1. δ-Aminolaevulate dehydratase (EC 4.2.1.24) was purified 80-fold from tobacco leaves and its properties were studied. 2. The enzyme had optimum pH7·4 in potassium phosphate buffer, Km6·25×10−4m at 37° and pH7·4, optimum temperature 45° and an activation energy of 11100 cal./mole. 3. The enzyme lost activity when prepared in the absence of cysteine, and this activity was only partly restored by the later addition of thiols. Reagents for thiol groups inactivated the enzyme. 4. Mg2+ was essential for activity, and EDTA and Fe2+ were inhibitory; Mn2+ was an activator or an inhibitor depending on the concentration.