Activation of lysine 2,3-aminomutase by S-adenosylmethionine.
Lysine 2,3-aminomutase, which catalyzes the interconversion of L-lysine and L-beta-lysine, is S-adenosyl-methionine-dependent, and the adenosyl-C-5' methylene group of this coenzyme mediates the transfer of hydrogen from C-3 of lysine to C-2 of beta-lysine. We here report experiments that address the mechanism by which S-adenosylmethionine activates lysine 2,3-aminomutase. We also describe an updated and improved purification procedure that produces enzyme with a specific activity substantially higher than that previously reported. Activation of the enzyme by less than 1 mol of S-adenosyl[1-14C]methionine/mol of subunits in the presence of lysine leads to the production of [14C] methionine in a kinetically biphasic process. After 1.8 min at 30 degrees C, 10% of the 14C is reisolated as [14C] methionine, and the cleavage increases to 19% after 10 min and to 51% after 40 min. Similar experiments with S-[8-14C]adenosylmethionine produce 5'-deoxy[14C]adenosine in amounts similar to the formation of methionine. The major radioactive products isolated in each case are [14C]methionine or 5'-deoxy[14C]adenosine, respectively, and unchanged 14C-labeled S-adenosylmethionine. These experiments support the hypothesis that activation of lysine 2,3-aminomutase involves a transfer of the 5'-deoxyadenosyl moiety from S-adenosylmethionine to another species associated with the enzyme, presumably another cofactor, to form an adenosyl cofactor that functions as the proximal, hydrogen abstracting species in the mechanism.
Institute for Enzyme Research, Graduate School, University of Wisconsin, Madison.
M L
ML
Moss
P A
PA
Frey
D000591:Amino Acid Isomerases / Q000302:isolation & purification / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology; D003839:Deoxyadenosines / Q000378:metabolism; D004789:Enzyme Activation; D019751:Intramolecular Transferases; D008715:Methionine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism*
D003839:Deoxyadenosines; C033714:5'-deoxyadenosine; D012436:S-Adenosylmethionine; D008715:Methionine; D000591:Amino Acid Isomerases; D019751:Intramolecular Transferases; C021518:lysine 2,3-aminomutase