Purification and characterization of sucrose-phosphate synthase from Prosopis juliflora

Abstract

Sucrose-phosphate synthase (SPS) was purified 4200-fold from the leaves of Prosopis juliflora and resulted in a final specific activity of 467 nkat mg^-1 protein. The M_r of the native enzyme was 443 by gel filtration. The activity was optimum at pH 7.5 in MOPS buffer. Kinetic data for the forward reaction and both products and dead end inhibition indicated that the enzyme reaction follows an ordered bi-bi mechanism. The purified preparation of SPS was activated by glucose-6-phosphate and inhibited by inorganic phosphate. Both had a large effect only on the K_m of UDPG with inorganic phosphate acting antagonistically to glucose-6-phosphate. The enzyme was inhibited by anions and activated by 25 mM MgCl₂. The enzyme showed marginal sensivity to -SH reagents, and the activity could be restored with DTT.