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[50] Nucleoside phosphotransferase from carrot

1978; Academic Press; Linguagem: Inglês

10.1016/s0076-6879(78)51052-5

1557-7988

Elinor F. Brunngraber,

Plant nutrient uptake and metabolism

This chapter describes the purification procedure of nucleoside phosphotransferase enzyme from carrot. The nucleoside phosphotransferase isolated from carrot is a protein carrying both transfer and hydrolytic functions. It catalyzes the phosphate transfer from a suitable donor, such as a 3' or 5' mononucleotide, to a nucleoside acceptor forming a new 5' nucleotide. In the absence of a suitable acceptor, the phosphate is released as inorganic phosphate. The transfer function is assayed by determining the amount of 5' nucleotide formed when the enzyme is incubated with a nucleoside and a suitable phosphate donor. The phosphatase activity is determined by the estimation of phosphorus. With more highly concentrated enzyme solutions, the enzyme should be diluted with buffer to give a concentration hydrolyzing less than 25% of the donor. The molecular weight of the protein is found to be near 44,000 by three different methods: gel filtration, sedimentation equilibrium, and sucrose density-gradient methods. A value of 38,000 is estimated from the amino acid composition.