title: Cyanobacterial hydrogenases: diversity, regulation and applications.
abstract: Cyanobacteria may possess two distinct nickel-iron (NiFe)-hydrogenases: an uptake enzyme found in N(2)-fixing strains, and a bidirectional one present in both non-N(2)-fixing and N(2)-fixing strains. The uptake hydrogenase (encoded by hupSL) catalyzes the consumption of the H(2) produced during N(2) fixation, while the bidirectional enzyme (hoxEFUYH) probably plays a role in fermentation and/or acts as an electron valve during photosynthesis. hupSL constitute a transcriptional unit, and are essentially transcribed under N(2)-fixing conditions. The bidirectional hydrogenase consists of a hydrogenase and a diaphorase part, and the corresponding five hox genes are not always clustered or cotranscribed. The biosynthesis/maturation of NiFe-hydrogenases is highly complex, requiring several core proteins. In cyanobacteria, the genes that are thought to affect hydrogenases pleiotropically (hyp), as well as the genes presumably encoding the hydrogenase-specific endopeptidases (hupW and hoxW) have been identified and characterized. Furthermore, NtcA and LexA have been implicated in the transcriptional regulation of the uptake and the bidirectional enzyme respectively. Recently, the phylogenetic origin of cyanobacterial and algal hydrogenases was analyzed, and it was proposed that the current distribution in cyanobacteria reflects a differential loss of genes according to their ecological needs or constraints. In addition, the possibilities and challenges of cyanobacterial-based H(2) production are addressed.
authors: IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal. pmtamagn@ibmc.up.pt
authors: Paula
authors: P
authors: Tamagnini
authors: Elsa
authors: E
authors: Leitão
authors: Paulo
authors: P
authors: Oliveira
authors: Daniela
authors: D
authors: Ferreira
authors: Filipe
authors: F
authors: Pinto
authors: David James
authors: DJ
authors: Harris
authors: Thorsten
authors: T
authors: Heidorn
authors: Peter
authors: P
authors: Lindblad
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D000458:Cyanobacteria / Q000201:enzymology*; D006859:Hydrogen / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D009586:Nitrogen Fixation; D011401:Promoter Regions, Genetic; D015202:Protein Engineering; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D006859:Hydrogen; D006864:Hydrogenase