If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: curcumin metabolism
|Superclasses:||Degradation/Utilization/Assimilation → Secondary Metabolites Degradation|
Curcumin and other curcuminoids are plant secondary metabolites produced by Curcuma longa (turmeric) (see MetaCyc pathway curcuminoid biosynthesis). Curcumin is the main yellow pigment of turmeric which is used as a spice and a pigment. In addition, curcumin has a range of medicinal properties including antioxidant, anti-inflammatory, anticancer and analgesic. Curcumin metabolism has been studied in humans and rodents and the production of reduced dihydro-, tetrahydro-, hexahydro- and octahydrocurcumin derivatives has been identified, with tetrahydrocurcumin and hexahydrocurcumin being the major products. These reduced curcumin derivatives may then be conjugated to form glucuronides, sulfates, or mixed glucuronides/sulfates. However, the mammalian enzymes and their encoding genes responsible for production of the reduced curcumin derivatives have not been identified. Tetrahydrocurcumin has been shown to have more potent antioxidative activity than curcumin (in [Hassaninasab11] and reviewed in [Osawa07]).
Intestinal microorganisms have also been shown to metabolize curcumin. Curcumin metabolizing microorganisms were found in samples of human feces and the organism with the highest curcumin converting activity was isolated, cultured and identified as Escherichia coli. High curcumin converting activity was also identified in Escherichia coli K-12 substr. DH10B whose genome sequence has been determined. The curcumin metabolizing enzyme was purified from extracts of this organism and used to identify its encoding gene. Following gene cloning and overexpression, the recombinant enzyme was purified and characterized. The results showed that E. coli gene yncB (annotated as predicted oxidoreductase, Zn-dependent and NAD(P)-binding) encoded the curcumin-converting enzyme and it was renamed curA [Hassaninasab11].
About This Pathway
The purified product of Escherichia coli gene curA was shown to catalyze the NADPH-dependent, sequential reduction of curcumin first to the stable intermediate dihydrocurcumin, and then to the final end product tetrahydrocurcumin. These compounds were identified by mass spectrometry techniques. How curcumin enters the E. coli cell and the fate of tetrahydrocurcumin in E. coli is not yet known. However, the optimum culture conditions for curcumin-converting enzyme formation in Escherichia coli K-12 substr. DH10B included the use of 0.03% curcumin as the sole carbon source and 0.3% yeast extract as nitrogen source, suggesting further metabolism of curcumin under these conditions. It has also been speculated that tetrahydrocurcumin produced by human or animal gut microorganisms may be used for various activities in the body [Hassaninasab11].
Hassaninasab11: Hassaninasab A, Hashimoto Y, Tomita-Yokotani K, Kobayashi M (2011). "Discovery of the curcumin metabolic pathway involving a unique enzyme in an intestinal microorganism." Proc Natl Acad Sci U S A 108(16):6615-20. PMID: 21467222
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
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