A CDPK type protein kinase is involved in rice SPS light modulation

• Published in: Physiologia plantarum Vol. 115; no. 2; pp. 183 - 189
• Main Authors: Pagnussat, Gabriela C., Fiol, Diego F., Salerno, Graciela L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01.06.2002; Blackwell
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Economic plant physiology; Enzymes; Fundamental and applied biological sciences. Psychology; Metabolism; Nutrition. Photosynthesis. Respiration. Metabolism; Plant physiology and development; Phosphates; Monocotyledones; Phosphorylation; Calcium; Metabolite; Glycosyltransferases; Sucrose-phosphate synthase; Cofactor; Cereal crop; Characterization; Oryza sativa; Regulation(control); Enzymatic activity; Gramineae; Light; Angiospermae; Calmodulin; Light effect; Purification; Enzyme; Transferases; Protein kinase; Hexosyltransferases; Spermatophyta; Catalyst activity
• ISSN: 0031-9317; 1399-3054
• DOI: 10.1034/j.1399-3054.2002.1150202.x

A protein kinase activity that can phosphorylate and inactivate rice (Oryza sativa) sucrose‐phosphate synthase (SPS; UDP‐glucose: d‐fructose‐6‐phosphate‐2‐glucosyl transferase, EC 2.4.1.14) was measured in extracts prepared from leaves exposed to light‐dark transitions. Enzyme activity present in extracts from dark leaves was about 5‐fold higher than the activity in extracts from leaves that had been collected in the light. The protein kinase (named R‐SPSK) was purified about 100‐fold from dark leaves and its biochemical properties were studied. The micromolar dependence of Ca2+ exhibited by R‐SPSK, and its response to calmodulin antagonists was similar to the properties associated with members of the plant Calcium‐Dependent Protein Kinase (CDPK) family. Two modulators of SPS activity, Pi and Glc‐6‐P, were examined for an effect on R‐SPSK. While Glc‐6‐P did not affect R‐SPSK activity, Pi drastically increased the kinase activity. Taken together, these data provide evidence that SPS may be regulated by a CDPK type protein‐kinase whose activity is modulated by light‐dark transitions and stimulated by Pi, the negative effector of SPS activity.