Keto-acid oxidoreductases in the anaerobic protozoa.
In anaerobes, decarboxylation of pyruvate is executed by the enzyme pyruvate:ferredoxin oxidoreductase, which donates electrons to ferredoxin. The pyruvate:ferredoxin oxidoreductase and its homologues utilise many alternative substrates in bacterial anaerobes. The pyruvate:ferredoxin oxidoreductase from anaerobic protozoa, such as Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica have retained this diversity in usage of alternative keto acids for energy production utilising a wide variety of substrates. In addition to this flexibility, both T. vaginalis and G. duodenalis have alternative enzymes that are active in metronidazole-resistant parasites and that do not necessarily involve donation of electrons to characterized ferredoxins. Giardia duodenalis has two oxoacid oxidoreductases, including pyruvate:ferredoxin oxidoreductase and T. vaginalis has at least three. These alternative oxoacid oxidoreductases apparently do not share homology with the characterized pyruvate:ferredoxin oxidoreductase in either organism. Independently, both G. duodenalis and T. vaginalis have retained alternative oxoacid oxidoreductase activities that are clearly important for the survival of these parasitic protists.
Upcroft
J A
JA
Queensland Institute of Medical Research, Brisbane. jacquiU@qimr.edu.au
Upcroft
P
P
D000693:Anaerobiosis; D000818:Animals; D004748:Entamoeba histolytica / Q000201:enzymology; D056890:Eukaryota / Q000201:enzymology*; D005872:Giardia / Q000201:enzymology; D007651:Keto Acids / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D014246:Trichomonas vaginalis / Q000201:enzymology
D007651:Keto Acids; D010088:Oxidoreductases