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Results 1 - 9 of 9
EC Number
General Information
Commentary
Reference
evolution
BchE and ChlA/AcsF are mainly identified in anoxygenic photosynthetic bacteria and plants, respectively. Some photosynthetic bacteria have either both or one of the two enzymes. The phylogenetic relationships imply that both chlE/bchE and chlA/acsF genes had been the MPE cyclase genes inherited by a cyanobacterial common ancestor, and chlE has been later lost in several lineages. The chlA gene has persisted in all cyanobacterial lineages. A gene duplication of chlA to form chlAI and chlAII appears to have occurred in an early phase of evolution of cyanobacteria. Phylogenetic trees of ChlE/BchE and ChlA/AcsF, cyanobacteria and photosynthetic bacteria
malfunction
bchE genes from Cyanothece strains PCC 7425 and PCC 7822 restore the photosynthetic growth and bacteriochlorophyll production in the bchE-lacking mutant of Rhodobacter capsulatus
metabolism
comparison of the presence of BchE and AcsF genes encoding oxygen-independent and oxygen-dependent magnesium-protoporphyrin IX monomethylester cyclase, EC 1.21.98.3 and EC 1.14.13.81, respectively, in Proteobacteria. All tested species of aerobic anoxygenic phototrophs contain acsF genes, but some of them also retain the bchE gene. In contrast to bchE phylogeny, the AcsF phylogeny is in good agreement with 16S inferred phylogeny. The AcsF gene occupies a conserved position inside the photosynthesis gene cluster, whereas the BchE location in the genome varies largely between the species
metabolism
proposed reaction mechanism for the Mg-protoporphyrin monomethyl ester-cyclase reaction starts with adenosylcobalamin forming the adenosyl radical, which leads to withdrawal of a hydrogen atom and formation of the benzylic-type 131-radical of Mg-protoporphyrin monomethyl ester. Withdrawal of an electron gives the 131-cation of Mg-protoporphyrin monomethyl ester. Hydroxyl ion attack on the cation gives 131-hydroxy-Mg-protoporphyrin monomethyl ester. Withdrawal of three hydrogen atoms leads successively to 131-keto-Mg-protoporphyrin monomethyl ester, its 132-Mg-protoporphyrin monomethyl ester, and cyclization to protochlorophyllide
physiological function
a BchE mutant is photosynthesis-deficient, produces bacteriochlorophyll only under high oxygenation and accumulates Mg-protoporphyrin monomethyl ester under low oxygenation and anaerobiosis. A double knockout mutant lacking both Bche and aerobic magnesium-protoporphyrin IX monomethyl ester [oxidative] cyclase AcsF is devoid of photosystem and accumulates Mg-protoporphyrin monomethyl ester under both conditions indicating the involvement of the two enzymes at the same step of the biosynthesis pathway. AcsF acts strictly under high oxygenation conditions, whereas BchE is involved when the oxygen tension drops
physiological function
expression of the bchE genes from Cyanothece strain PCC 7425 restores the photosynthetic growth and bacteriochlorophyll production in a bchE-lacking mutant of Rhodobacter capsulatus
physiological function
expression of the bchE genes from Cyanothece strain PCC 7822 restores the photosynthetic growth and bacteriochlorophyll production in a bchE-lacking mutant of Rhodobacter capsulatus
physiological function
expression of the gene restores the photosynthetic growth and bacteriochlorophyll production in a bchE lacking mutant of Rhodobacter capsulatus. Significant amounts of Mg-protoporphyrin IX monomethyl ester and 3,8-divinyl protochlorophyllide and monovinyl protochlorophyllide are identified in the transconjugant
physiological function
insertion mutant are defective in converting magnesium-protoporphyrin monomethyl ester to protochlorophyllide
Results 1 - 9 of 9