Biomaterial Database

5'-Methylthioadenosine nucleosidase. Purification and characterization of the enzyme from Lupinus luteus seeds. 1981

A B Guranowski, and P K Chiang, and G L Cantoni

5'-Methylthioadenosine nucleosidase (EC 3.2.2.9), 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).

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D010430	Pentosyltransferases	Enzymes of the transferase class that catalyze the transfer of a pentose group from one compound to another.
D011683	Purine-Nucleoside Phosphorylase	An enzyme that catalyzes the reaction between a purine nucleoside and orthophosphate to form a free purine plus ribose-5-phosphate. EC 2.4.2.1.	Inosine Phosphorylase,Nicotinamide Riboside Phosphorylase,Purine Nucleoside Phosphorylases,Nucleoside Phosphorylases, Purine,Phosphorylase, Inosine,Phosphorylase, Nicotinamide Riboside,Phosphorylase, Purine-Nucleoside,Phosphorylases, Purine Nucleoside,Purine Nucleoside Phosphorylase,Riboside Phosphorylase, Nicotinamide
D000241	Adenosine	A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.	Adenocard,Adenoscan
D012639	Seeds	The encapsulated embryos of flowering plants. They are used as is or for animal feed because of the high content of concentrated nutrients like starches, proteins, and fats. Rapeseed, cottonseed, and sunflower seed are also produced for the oils (fats) they yield.	Diaspores,Elaiosomes,Embryos, Plant,Plant Embryos,Plant Zygotes,Zygotes, Plant,Diaspore,Elaiosome,Embryo, Plant,Plant Embryo,Plant Zygote,Seed,Zygote, Plant
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D013872	Thionucleosides	Nucleosides in which the base moiety is substituted with one or more sulfur atoms.