Demonstration of 5'-methylthioadenosine phosphorylase activity in various rat tissues. Some properties of the enzyme from rat lung.
An enzyme (5'-methylthioadenosine phosphorylase) that catalyzes the phosphorolytic cleavage of 5'-methylthioadenosine to 5-methylthioadenosine to 5-methylthioribose-1-phosphate and adenine was found in various rat tissues. Liver and lung had the highest enzyme activities and heart the lowest, most of the activity (greater than 90%) was recovered in soluble tissue fractions. The enzyme from rat lung was purified about 30-fold by pH treatment (NH4)2SO4 fractionation, and gel filtration. The enzyme did not require an added metal-ion for activity, and was not inhibited by EDTA. Many compounds were tested for their inhibitory effects; of these, ribose 1-phosphate, 2-deoxyribose 1-phosphate, fructose 1-phosphate, adenine and guanine were shown to inhibit. Kinetic patterns on reciprocal plots were linear as a function of the concentration of either 5'-methylthioadenosine or phosphate. More detailed kinetic studies suggested that the rat lung 5'-methylioadenosine phosphorylase catalyzes an equilibrium-ordered reaction, and that 5'-methylthioadenosine is the first substrate to bind and 5-methylthioribose-1-phosphate is the first product to be released.
D000241:Adenosine / Q000031:analogs & derivatives; D000818:Animals; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008168:Lung / Q000201:enzymology*; D008297:Male; D010430:Pentosyltransferases / Q000378:metabolism*; D011683:Purine-Nucleoside Phosphorylase / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D014018:Tissue Distribution
D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase; D000241:Adenosine