Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.1.14 (SPS)
 813 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Annual changes of activity of sucrose-phosphate synthase (SPS) from spruce (Picea abies [L.] Karst.) needles were studied with respect to three regulatory levels: metabolic fine control, covalent modification (phosphorylation), and protein amount. Glucose-6-phosphate served as an allosteric activator of spruce SPS by shifting the Michaelis constant for the substrate fructose-6-phosphate from 4.2 to 0.59 mM, whereas inorganic phosphate competitively inhibited this activation. The affinity for the other substrate, UDP-glucose, was unaffected. Incubation of the crude extract with ATP resulted in a time- and concentration-dependent decrease of the maximal velocity of SPS. This inactivation was sensitive to staurosporine, a potent protein kinase inhibitor, indicating the participation of a protein kinase. Probing SPS protein with heterologous antibodies showed that the subunit of spruce SPS is an approximately 139-kD protein and that changes in the extractable activity during the course of a year were correlated with the amount of SPS protein. High SPS activities in winter were paralleled by increased levels of the activator glucose-6-phosphate and the substrate fructose-6-phosphate, indicating a high capacity for sucrose synthesis that may be necessary to maintain photosynthetic CO2 fixation in cold-hardened spruce needles.
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PMID:Coarse and Fine Control and Annual Changes of Sucrose-Phosphate Synthase in Norway Spruce Needles. 1222 18