Metabolism of Cytokinin: Deribosylation of Cytokinin Ribonucleoside by Adenosine Nucleosidase from Wheat Germ Cells 1
AUTOR(ES)
Chen, Chong-Maw
RESUMO
Adenosine nucleosidase (adenosine ribohydrolase, EC 3.2.2.7) which catalyzes the deribosylation of N6-(Δ2-isopentenyl)adenosine and adenosine to form the corresponding bases was partially purified from wheat germ. This enzyme (molecular weight 59,000 ± 3,000) deribosylates the ribonucleosides at an optimum pH of 4.7 Km values for the cytokinin nucleoside and adenosine are 2.38 and 1.43 micromolar, respectively, in 50 millimolar Tris-citrate buffer (pH 4.7) at 30 C. The presence of adenosine and other cytokinin nucleosides inhibited the hydrolysis of N6-(Δ2-isopentenyl)adenosine but this reaction was insensitive to guanosine, uridine, or 3′-deoxyadenosine. It is hypothesized that an adequate level of “active cytokinin” in plant cells may be provided through the deribosylation of cytokinin riboside in concert with other cytokinin metabolic enzymes.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=426037Documentos Relacionados
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