Metabolism of cytokinin: Phosphoribosylation of cytokinin bases by adenine phosphoribosyltransferase from wheat germ |
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Authors: | Chong-Maw Chen Debra K Melitz Fred W Clough |
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Institution: | Department of Life Science and Biomedical Research Institute, University of Wisconsin-Parkside, Kenosha, Wisconsin 53141 USA |
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Abstract: | Adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase EC 2.4.2.8) which catalyzes the phosphoribosylation of cytokinin bases and adenine to form the corresponding nucleotides were partially purified from the cytosol of wheat (Triticum aestivum) germ. This enzyme (molecular weight, 23,000 ± 500) phosphoribosylates the bases at an optimum Mg2+ concentration of 5 mm and optimum pH of 7.5 (50 mm Tris-HCl buffer). Km values for N6-(Δ2-isopentenyl)adenine, N6-furfuryladenine, N6-benzyladenine, and adenine are 130, 110, 154, and 74 μm, respectively, in 50 mm Tris-HCl buffer (pH 7.5) at 37 °C. Hypoxanthine and guanine are not substrates for the enzyme. In concerting with other cytokinin metabolic enzymes, this enzyme may play a significant role in maintaining the supply of adequate levels of “active cytokinin.” |
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Keywords: | Author to whom all correspondence should be addressed |
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