Sucrose synthase from wheat leaves. Comparison with the wheat germ enzyme

Sucrose synthase (UDP glucose: D-fructose-2-glucosyl transferase, EC 2.4.1.13) was partially purified from wheat ( Triticum aestivum L. cv. San Agustin INTA) leaves and its properties compared with the wheat germ enzyme. The leaf enzyme moved faster in polyacrylamide gel electrophoresis, was more sensitive to SH reagents and crossreacted more slowly with antibody prepared towards the germ enzyme. Kinetic constants were of the same order for all substrates. UDP was a strong inhibitor of the synthesis reaction. MgCl₂ stimulated this reaction and partially reversed UDP inhibition. Molecular weight determined by gel filtration was 380 and 370 kdalton for the leaf and germ enzymes respectively. Both enzymes presented forms of higher molecular weight estimated to around 800 and 1000 kdalton. Neither sucrose synthase from leaves nor from germ were affected by fructose 6-P, fructose 1,6—P₂, glucose 1—P, glucose 6—P, fructose 2,6—P₂ and cAMP.