Abstract
Summary Adenine phosphoribosyltransferase (EC 2.4.2.7), one of the purine salvage enzymes, was extracted from cultured cells of Catharanthus roseus and purified by fractionation with ammonium sulphate and affinity chromatography of AMP-agarose. Catharanthus APRTase required Mg 2+ for its activity. The pH optimum was pH 7.6–8.0. The Km values for adenine and PRPP at optimal pH (7.6) were 7.0 and 9.6 μM, respectively. The values at physiological pH (7.2) were 6.6 μM for adenine and 9.0 μM for PRPP. APRTase activity was inhibited by AMP. The inhibition of AMP was competitive with PRPP, but little or no effect of other purine and pyrimidine nucleotides was observed. The activity of adenine salvage in Catharanthus cells in vivo seems to be regulated by the intracellular concentration and availability of adenine, PRPP and AMP.
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