Muconolactone isomerase of the 3-oxoadipate pathway catalyzes dechlorination of 5-chloro-substituted muconolactones.
An enzyme of Alcaligenes eutrophus JMP 134 which catalyzes dechlorination of (4R, 5R)- and (4R,5S)-5-chloro-3-methyl- and (4R, 5S)-5-chloromuconolactone of principally 3-methyl-trans-, 3-methyl-cis-dienelactone and cis-dienelactone, respectively, was purified to homogeneity. The enzyme was identified as muconolactone isomerase on the basis of its high activity with muconolactone and on its high degree of sequence similarity with previously described muconolactone isomerases. Molecular mass determinations of the highly hydrophobic and heat-resistant enzyme indicated a decameric structure involving a single 10.100-kDa subunit similar to that of muconolactone isomerase of Pseudomonas putida. Kinetic analysis showed cooperative effects between the subunits during conversion of (4R, 5S)-5-chloro-3 -methylmuconolactone. (4R, 5S)-5-chloromuconolactone was the preferred substrate, over the natural substrate (4S)-muconolactone. The (4S, 5S)-structure was found to be an inhibitor of (4R, 5R)-5-chloro-3-methylmuconolactone transformation. Methylsubstitution of the substrate results in a higher affinity for the enzyme, but a drastically lower velocity, resulting in a lower specificity constant.
Prucha
M
M
Department of Microbiology, National Research Centre for Biotechnology, Braunschweig, Germany.
Peterseim
A
A
Timmis
K N
KN
Pieper
D H
DH
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D000272:Adipates / Q000378:metabolism; D000421:Alcaligenes / Q000201:enzymology* / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D019748:Carbon-Carbon Double Bond Isomerases; D006863:Hydrogen-Ion Concentration; D007535:Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D007783:Lactones / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000272:Adipates; D001426:Bacterial Proteins; D007783:Lactones; C027316:3-oxoadipic acid; C088142:5-chloromuconolactone; D007535:Isomerases; D019748:Carbon-Carbon Double Bond Isomerases; C100087:muconolactone delta-isomerase; D015107:4-Butyrolactone