A FUNCTIONAL ROLE OF METAL IONS IN A CLASS 2 ALDOLASE

A crucial role of the metal ion in the catalytic activity of yeast aldolase has been demonstrated. Zinc can be removed from the native enzyme resulting in an inactive apoenzyme. The activity can be reconstituted by addition of Zn2+ or by certain ions of the first transition period, namely C2+, Ni2+, Mn2+, and Fe2+. The Zn2+ protein has thehighest specific activity; the other metal ions restore the enzymatic activity to varying de grees.A number of other metal ions (Cu2+, Hg2+, Cd2+, Mg2+, and Fe3+) fail to restore activity to any measurable extent. All active metalloaldolases exhibit similar Km values for fructose diphosphate and are stimulated by K+ ion. © 1969, American Chemical Society. All rights reserved.