Topography and Function of Golgi Uridine-5[prime]-Diphosphatase from Pea Stems.

AUTOR(ES)

Orellana, A.

RESUMO

Golgi UDPase is an enzyme that has been shown to function in polysaccharide biosynthesis, but its role in this process is not yet clear. In this study we identified Golgi UDPase activity in pea (Pisum sativum) stems and differentiated it from another UDPase activity. We demonstrated that Golgi UDPase is an integral membrane protein, based on specific partitioning of this activity into Triton X-114. Analysis of its topology using sealed, right-side-out Golgi vesicles and treatment with proteinase K suggested that its active site faces the Golgi lumen. Studies aimed at understanding the function of Golgi UDPase by incubating Golgi vesicles with [beta]-32P]UDP-glucose (Glc) to generate [beta]-32P]UDP upon Glc transfer in situ showed that 32Pi, but not [beta]-32P]UDP, was formed, suggesting that UDPase quickly hydrolyzed the UDP formed during Glc polymerization. We found that the Golgi UDPase was highly active in the elongating region of the third internode, whereas no activity was detected in the first and second internodes of etiolated pea seedlings. These results suggest that UDPase removes the UDP formed during Glc polymerization and could be important in the mechanism of polysaccharide biosynthesis.

Documentos Relacionados

• Metabolism of Uridine 5′-Diphosphate-Glucose in Golgi Vesicles from Pea Stems1
• A Xyloglucan-Specific Endo-1,4-[beta]-Glucanase Isolated from Auxin-Treated Pea Stems.
• Topography of glycosylation in yeast: characterization of GDPmannose transport and lumenal guanosine diphosphatase activities in Golgi-like vesicles.
• Structure and Function of the Golgi Complex in Rice Cells (II. Purification and Characterization of Golgi Membrane-Bound Nucleoside Diphosphatase).
• Location of light-repressible, small GTP-binding protein of the YPT/rab family in the growing zone of etiolated pea stems.