Pieper, Dietmar H.Stadler-Fritzsche, KarinKnackmuss, Hans-JoachimEngesser, Karl-HeinrichBruce, Neil C.Cain, Ronald B.2012-08-222016-03-312012-08-222016-03-311990371054478http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-76458http://elib.uni-stuttgart.de/handle/11682/8033http://dx.doi.org/10.18419/opus-80164-Carboxymethyl-4-methylbut-2-en-4-olide (4-methyl-2-enelactone) isomerase, transforming 4-methyl-2-enelactone to 3-methyl-2-enelactone, was purified from a derivative strain of Pseudomonas sp. B13, named B13 FR1, carrying the plasmid pFRC2OP. This plasmid contained the isomerase gene cloned from Alcaligenes eutrophus JMP 134, which uses 4-methyl-2-enelactone as a carbon source. The enzyme consists of a single peptide chain of Mr 40,000 as judged by SDS/PAGE. In addition to 4-methyl-2-enelactone, the putative reaction intermediate, 1-methyl-3,7-dioxo-2,6-dioxy-bicyclo[3.3.0]octane (1-methylbislactone), was a substrate for the enzyme, but kinetic data presented did not favour its role as a reaction intermediate. Isomeric methyl-substituted 4-carboxymethylbut-2-en-4-olides were neither substrates nor inhibitors. Possible reaction mechanisms are discussed.eninfo:eu-repo/semantics/openAccessAlcaligenes eutrophus , Brenzcatechin570article