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Effect of Metal Cations on Aldolase from Leaves of Zea mays L. Seedlings¹

Aldolase prepared from 7- to 10-day-old Zea mays L. leaves was assayed for its response to metal cations. Monovalent cations at concentrations up to 0.2 M and divalent cations at concentrations up to 0.04 M had no stimulatory effect on aldolase activity. Aldolase was completely inhibited by Zn⁺⁺ and Co⁺⁺ at 0.04 M, 60% by Fe⁺⁺ 20% by Mn⁺⁺, and 0% by Ca⁺⁺ or Mg⁺⁺. It was inhibited slightly by NH₄⁺ above 0.1 M, but not by K⁺ Rb⁺, Cs⁺, Li⁺, or Na⁺. Cyanide and a,á-dipyridyl were inhibitory to aldolase above 5 x 10^–3 M, but ethylenediaminetetraacetic acid, 2,3-dimercapto-l-propanol, and pyrophosphate were not. o-Phenanthroline inhibited aldolase below as well as above 5 x 10^–3 M.

Aldolase was also prepared from corn seedlings grown 14 days in complete, minus-K, and minus-Zn nutrient solutions. Aldolase activity was lower in preparations from K- and Zn-deficient plants than in preparations from nondeficient plants. K⁺ and Zn⁺⁺ added in vitro to aldolase from K- and Zn-deficient plants did not stimulate the enzyme. The reduced aldolase activity found in mineral-deficient plants was attributed to reduced protein synthesis rather than to a requirement for metal cations for aldolase activity.

² Research Chemist, Crops Research Divisions, ARS, USDA, Wooster, Ohio.

Received for publication May 24, 1966.