Formation of Protoanemonin from 2-Chloro-cis,cis-Muconate by the Combined Action of Muconate Cycloisomerase and Muconolactone Isomerase
AUTOR(ES)
Skiba, Anke
FONTE
American Society for Microbiology
RESUMO
Muconate cycloisomerases are known to catalyze the reversible conversion of 2-chloro-cis,cis-muconate by 1,4- and 3,6-cycloisomerization into (4S)-(+)-2-chloro- and (4R/5S)-(+)-5-chloromuconolactone. 2-Chloromuconolactone is transformed by muconolactone isomerase with concomitant dechlorination and decarboxylation into the antibiotic protoanemonin. The low kcat for this compound compared to that for 5-chloromuconolactone suggests that protoanemonin formation is of minor importance. However, since 2-chloromuconolactone is the initially predominant product of 2-chloromuconate cycloisomerization, significant amounts of protoanemonin were formed in reaction mixtures containing large amounts of muconolactone isomerase and small amounts of muconate cycloisomerase. Such enzyme ratios resemble those observed in cell extracts of benzoate-grown cells of Ralstonia eutropha JMP134. In contrast, cis-dienelactone was the predominant product formed by enzyme preparations, in which muconolactone isomerase was in vitro rate limiting. In reaction mixtures containing chloromuconate cycloisomerase and muconolactone isomerase, only minute amounts of protoanemonin were detected, indicating that only small amounts of 2-chloromuconolactone were formed by cycloisomerization and that chloromuconate cycloisomerase actually preferentially catalyzes a 3,6-cycloisomerization.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=135365Documentos Relacionados
- Conversion of 2-chloro-cis,cis-muconate and its metabolites 2-chloro- and 5-chloromuconolactone by chloromuconate cycloisomerases of pJP4 and pAC27.
- Inability of muconate cycloisomerases to cause dehalogenation during conversion of 2-chloro-cis,cis-muconate.
- Mechanism of Chloride Elimination from 3-Chloro- and 2,4-Dichloro-cis,cis-Muconate: New Insight Obtained from Analysis of Muconate Cycloisomerase Variant CatB-K169A†
- 3-Carboxy-cis,cis-muconate lactonizing enzyme from Neurospora crassa: an alternate cycloisomerase motif.
- Characterization of muconate and chloromuconate cycloisomerase from Rhodococcus erythropolis 1CP: indications for functionally convergent evolution among bacterial cycloisomerases.