5'-Methylthioadenosine nucleosidase. Purification and characterization of the enzyme from Lupinus luteus seeds

Eur J Biochem. 1981 Feb;114(2):293-9. doi: 10.1111/j.1432-1033.1981.tb05148.x.


5'-Methylthioadenosine nucleosidase (EC, the enzyme which catalyzes hydrolytic cleavage of 5'-methylthioadenosine with the formation of adenine and 5'-methylthioribose, has been purified to homogeneity from Lupinus luteus seeds. The nucleosidase has a native molecular weight of 62 000 and consists of two identical subunits, as judged by gel filtration and dodecylsulfate/polyacrylamide gel electrophoresis. The nucleosidase exhibits highest specificity towards the natural substrate with a Km of 4.1 X 10(-7) M for 5'-methylthioadenosine. It does not cleave adenine from S-adenosylhomocysteine. Among the synthetic analogs of 5'-methylthioadenosine tested, eleven compounds appear to be able to substitute as substrates. Furthermore, the enzyme can liberate hypoxanthinine from six inosyl (deaminated) derivatives obtained by enzymatic deamination of 5'-methylthioadenosine and its synthetic analogs. The Km for 5'-methylthioinosine is 55 microM, and the maximal velocity about 50-times lower than for 5'-methylthioadenosine. The reaction catalyzed by the nucleosidase can be inhibited by adenine (Ki = 11 microM), 3-deazaadenine (Ki = 19 microM), and 9-erythro(2-hydroxyl-3-nonyl)adenine (ki = 37 microM).

MeSH terms

  • Adenosine / analogs & derivatives
  • Adenosine / isolation & purification
  • Adenosine / metabolism
  • Kinetics
  • Molecular Weight
  • Pentosyltransferases / isolation & purification*
  • Purine-Nucleoside Phosphorylase / isolation & purification*
  • Purine-Nucleoside Phosphorylase / metabolism
  • Seeds / enzymology*
  • Substrate Specificity
  • Thionucleosides / isolation & purification
  • Thionucleosides / metabolism


  • Thionucleosides
  • 2-methylthioadenosine
  • Pentosyltransferases
  • Purine-Nucleoside Phosphorylase
  • 5'-methylthioadenosine phosphorylase
  • Adenosine