English Journal

The C-terminal domain of CblD interacts with CblC and influences intracellular cobalamin partitioning.

Gherasim C, Hannibal L, Rajagopalan D, Jacobsen DW, Banerjee R.Author information Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-0600, USA.AbstractMutations in cobalamin or B12 trafficking genes needed for cofactor assimilation and targeting lead to inborn errors of cobalamin metabolism. The gene corresponding to one of these loci, cblD, affects both the mitochondrial and cytoplasmic pathways for B12 processing. We have demonstrated that fibroblast cell lines from patients with mutations in CblD, can dealkylate exogenously supplied methylcobalamin (MeCbl), an activity catalyzed by the CblC protein, but show imbalanced intracellular partitioning of the cofactor into the MeCbl and 5'-deoxyadenosylcobalamin (AdoCbl) pools. These results confirm that CblD functions downstream of CblC in the cofactor assimilation pathway and that it plays an important role in controlling the traffic of the cofactor between the competing cytoplasmic and mitochondrial routes for MeCbl and AdoCbl synthesis, respectively. In this study, we report the interaction of CblC with four CblD protein variants with variable N-terminal start sites. We demonstrate that a complex between CblC and CblD can be isolated particularly under conditions that permit dealkylation of alkylcobalamin by CblC or in the presence of the corresponding dealkylated and oxidized product, hydroxocobalamin (HOCbl). A weak CblC·CblD complex is also seen in the presence of cyanocobalamin. Formation of the CblC·CblD complex is observed with all four CblD variants tested suggesting that the N-terminal 115 residues missing in the shortest variant are not essential for this interaction. Furthermore, limited proteolysis of the CblD variants indicates the presence of a stable C-terminal domain spanning residues ∼116-296. Our results are consistent with an adapter function for CblD, which in complex with CblC·HOCbl, or possibly the less oxidized CblC·cob(II)alamin, partitions the cofactor between AdoCbl and MeCbl assimilation pathways.
Biochimie.Biochimie.2013 May;95(5):1023-32. doi: 10.1016/j.biochi.2013.02.003. Epub 2013 Feb 14.
Mutations in cobalamin or B12 trafficking genes needed for cofactor assimilation and targeting lead to inborn errors of cobalamin metabolism. The gene corresponding to one of these loci, cblD, affects both the mitochondrial and cytoplasmic pathways for B12 processing. We have demonstrated that fibro
PMID 23415655

Characterisation of a desmosterol reductase involved in phytosterol dealkylation in the silkworm, Bombyx mori.

Ciufo LF, Murray PA, Thompson A, Rigden DJ, Rees HH.Author information Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.AbstractMost species of invertebrate animals cannot synthesise sterols de novo and many that feed on plants dealkylate phytosterols (mostly C(29) and C(28)) yielding cholesterol (C(27)). The final step of this dealkylation pathway involves desmosterol reductase (DHCR24)-catalysed reduction of desmosterol to cholesterol. We now report the molecular characterisation in the silkworm, Bombyx mori, of such a desmosterol reductase involved in production of cholesterol from phytosterol, rather than in de novo synthesis of cholesterol. Phylogenomic analysis of putative desmosterol reductases revealed the occurrence of various clades that allowed for the identification of a strong reductase candidate gene in Bombyx mori (BGIBMGA 005735). Following PCR-based cloning of the cDNA (1.6 kb) and its heterologous expression in Saccharomyces cerevisae, the recombinant protein catalysed reduction of desmosterol to cholesterol in an NADH- and FAD-dependent reaction.Conceptual translation of the cDNA, that encodes a 58.9 kDa protein, and database searching, revealed that the enzyme belongs to an FAD-dependent oxidoreductase family. Western blotting revealed reductase protein expression exclusively in the microsomal subcellular fraction and primarily in the gut. The protein is peripherally associated with microsomal membranes. 2D-native gel and PAGE analysis revealed that the reductase is part of a large complex with molecular weight approximately 250 kDa. The protein occurs in midgut microsomes at a fairly constant level throughout development in the last two instars, but is drastically reduced during the wandering stage in preparation for metamorphosis. Putative Broad Complex transcription factor-binding sites detectable upstream of the DHCR24 gene may play a role in this down-regulation.
PloS one.PLoS One.2011;6(6):e21316. doi: 10.1371/journal.pone.0021316. Epub 2011 Jun 27.
Most species of invertebrate animals cannot synthesise sterols de novo and many that feed on plants dealkylate phytosterols (mostly C(29) and C(28)) yielding cholesterol (C(27)). The final step of this dealkylation pathway involves desmosterol reductase (DHCR24)-catalysed reduction of desmosterol to
PMID 21738635

Formation, repair, and genotoxic properties of bulky DNA adducts formed from tobacco-specific nitrosamines.

Peterson LA.Author information Division of Environmental Health Sciences, Masonic Cancer Center, Mayo Mail Code 806, 420 Delaware St SE, Minneapolis, MN 55455, USA.Abstract4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are tobacco-specific nitrosamines present in tobacco products and smoke. Both compounds are carcinogenic in laboratory animals, generating tumors at sites comparable to those observed in smokers. These Group 1 human carcinogens are metabolized to reactive intermediates that alkylate DNA. This paper focuses on the DNA pyridyloxobutylation pathway which is common to both compounds. This DNA route generates 7-[4-(3-pyridyl)-4-oxobut-1-yl]-2'-deoxyguanosine, O(2)-[4-(3-pyridyl)-4-oxobut-1-yl]-2'-deoxycytosine, O(2)-[4-(3-pyridyl)-4-oxobut-1-yl]-2'-deoxythymidine, and O(6)-[4-(3-pyridyl)-4-oxobut-1-yl]-2'-deoxyguanosine as well as unstable adducts which dealkylate to release 4-hydroxy-1-{3-pyridyl)-1-butanone or depyriminidate/depurinate to generate abasic sites. There are multiple repair pathways responsible for protecting against the genotoxic effects of these adducts, including adduct reversal as well as base and nucleotide excision repair pathways. Data indicate that several DNA adducts contribute to the overall mutagenic properties of pyridyloxobutylating agents. Which adducts contribute to the carcinogenic properties of this pathway are likely to depend on the biochemistry of the target tissue.
Journal of nucleic acids.J Nucleic Acids.2010 Sep 5;2010. pii: 284935. doi: 10.4061/2010/284935.
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are tobacco-specific nitrosamines present in tobacco products and smoke. Both compounds are carcinogenic in laboratory animals, generating tumors at sites comparable to those observed in smokers. These Group 1 human
PMID 20871819

Japanese Journal

リグニン側鎖-芳香核間結合の選択的開裂

Funaoka Masamitsu,Abe Isao,船岡正光,阿部勲
三重大學農學部演習林報告 = Bulletin of the Mie University Forests 15, 97-109, 1987-02-01
… The impotant characteristic of NE-method is to dealkylate diphenylmethane type structural units involving lignin phenyl nuclei following the formation of such structures by lignin in a high yield by NE-method. …
NAID 120000949233

赤血球による薬物のN脱エチル化反応について

松沢佑次,山本章,和田文雄
臨床化学シンポジウム 17(0), 116-121, 1978
… We investigated the possibility that red blood cells dealkylate 4, 4' -bis(β -diethylamino-ethoxy) α, β-diethyldiphenylethane (DH), which caused a peculiar drug-induced lipidosis. …
NAID 130003355113