Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the anaerobic fungus Neocallimastix sp. L2 fermentation of glucose proceeds via the Embden-Meyerhof-Parnas pathway. Enzyme activities leading to the formation of succinate, lactate, ethanol, and formate are associated with the cytoplasmic fraction. The enzymes 'malic enzyme,' NAD(P)H:ferredoxin oxidoreductase, pyruvate:ferredoxin oxidoreductase, hydrogenase, acetate:succinate CoA transferase and succinate thiokinase leading to the formation of H2,CO2, acetate, and ATP are localized in microbodies. Thus, these organelles are identified as hydrogenosomes. In addition, the microbodies contain the O2-scavenging enzymes NADH- and NADPH oxidase, while NAD(P)H peroxidase, catalase, or superoxide dismutase could not be detected. In cell-free extracts from zoospores of Neocallimastix sp. L2 the specific activities of hydrogenosomal enzymes as well as the quantities of these proteins are 2- to 6-fold higher than in mycelium extracts. These findings suggest that hydrogenosomes perform an important role--especially in zoospores--as H2-evolving, ATP-generating and O2-scavenging organelles.
 ...
PMID:Characterization of hydrogenosomes and their role in glucose metabolism of Neocallimastix sp. L2. 825 82

The microaerophilic flagellated protist Giardia intestinalis, the commonest protozoal agent of intestinal infections worldwide, is of uncertain phylogeny, but is usually regarded as the earliest branching of the eukaryotic clades. Under strictly anaerobic conditions, a mass spectrometric investigation of gas production indicated a low level of generation of dihydrogen (2 nmol x min(-1) per 10(7) organisms), about 10-fold lower than that in Trichomonas vaginalis under similar conditions. Hydrogen evolution was O2 sensitive, and inhibited by 100 microM metronidazole. Fluorescent labelling of G. intestinalis cells using monoclonal antibodies to typical hydrogenosomal enzymes from T. vaginalis (malate enzyme, and succinyl-CoA synthetase alpha and beta subunits), and to the large-granule fraction (hydrogenosome-enriched, also from T. vaginalis) gave no discrete localization of epitopes. Cell-free extracts prepared under anaerobic conditions showed the presence of a CO-sensitive hydrogenase activity. This first report of hydrogen production in a eukaryote with no recognizable hydrogenosomes raises further questions about the early branching status of G. intestinalis; the physiological characterization of its hydrogenase, and its recently elucidated gene sequence, will aid further phylogenetic investigations.
 ...
PMID:Giardia intestinalis, a eukaryote without hydrogenosomes, produces hydrogen. 1188 7

Histomonas meleagridis is a trichomonad species that undergoes a flagellate-to-amoeba transformation during tissue invasion and causes a serious disease in gallinaceous birds (blackhead disease or histomoniasis). Living in the avian cecum, the flagellated form can be grown in vitro in the presence of an ill-defined bacterial flora. Its cytoplasm harbours numerous spherical bodies which structurally resemble hydrogenosomes. To test whether these organelles may be involved in anaerobic metabolism, we undertook the identification of H. meleagridis genes encoding some potentially conserved hydrogenosomal enzymes. The strategy was based on several PCR amplification steps using primers designed from available sequences of the phylogenetically-related human parasite Trichomonas vaginalis. We first obtained a C-terminal sequence of an iron-hydrogenase homologue (Hm_HYD) with typical active site signatures (H-cluster domain). Immunoelectron microscopy with anti-Hm_HYD polyclonal antibodies showed specific gold labelling of electron-dense organelles, thus confirming their hydrogenosomal nature. The whole genes encoding a malic enzyme (Hm_ME) and the alpha-subunit of a succinyl coenzyme A synthetase (Hm_alpha-SCS) were then identified. Short N-terminal presequences for hydrogenosomal targeting were predicted in both proteins. Anti-Hm_ME and anti-Hm_alpha-SCS antisera provided immunofluorescence staining patterns of H. meleagridis cytoplasmic granules similar to those observed with anti-Hm_HYD antiserum or mAb F5.2 known to react with T. vaginalis hydrogenosomes. Hm_ME, Hm_alpha-SCS and Hm_HYD were also detected as reactive bands on immunoblots of proteins from purified hydrogenosomes. Interestingly, anti-Hm_alpha-SCS staining of the cell surface in non-permeabilised parasites suggests a supplementary role for SCS in cytoadherence, as previously demonstrated in T. vaginalis.
 ...
PMID:First molecular characterisation of hydrogenosomes in the protozoan parasite Histomonas meleagridis. 1769 79

Blastocystis hominis is an anaerobic parasite of the human intestinal tract belonging to the Stramenopile group. Using genome sequencing project data, we describe here the complete sequence of a 29,270-bp circular DNA molecule that presents mitochondrial features (such as oxidative phosphorylation complex I subunits) but lacks complexes III, IV and V. Transmission electron microscopy analyses reveal that this molecule, as well as mitochondrial (NADH:ubiquinone oxidoreductase subunit 7 (NAD7), beta-succinyl-CoA synthetase (beta-SCS)) and hydrogenosomal (pyruvate ferredoxin oxido-reductase (PFOR), iron-hydrogenase) proteins, are located within double-membrane surrounded-compartments known as mitochondria-like organelles (MLOs). As there is no evidence for hydrogen production by this organism, we suggest that MLOs are more likely anaerobic mitochondria.
 ...
PMID:Complete circular DNA in the mitochondria-like organelles of Blastocystis hominis. 1869 56