Assays of Methylenetetrahydrofolate Reductase and Methionine Synthase Activities by Monitoring 5-Methyltetrahydrofolate and Tetrahydrofolate Using High-Performance Liquid Chromatography with Fluorescence Detection

Effects of Betaine Supplementation and Choline Deficiency on Folate Deficiency-Induced Hyperhomocysteinemia in Rats

“…The concentrations of betaine and DMG in the liver were measured by HPLC following Laryea et al ( 31 ) and the concentration of serine in the liver was measured by an amino acid autoanalyzer (Model L-8500; Hitachi). The activity of MS in the liver was measured following Huang et al ( 32 ). The activity of BHMT in the liver was measured following Finkelstein and Mudd ( 33 ), but HPLC was used in the assay of the reaction product, DMG, following Laryea et al ( 31 ).…”

Occurrence of Pseudovitamin B12 and Its Possible Function as the Cofactor of Cobalamin-Dependent Methionine Synthase in a Cyanobacterium Synechocystis sp. PCC6803

“…Vitamin B 12 or cyanocobalamin (B 12 ) has a corrin ring in which the central cobalt atom is coordinated by tetra-pyrroles. Two axial (upper and lower) ligands also coordinate the cobalt atom.…”

“…Two axial (upper and lower) ligands also coordinate the cobalt atom. The lower ligand of B 12 molecule contains a cobalt-coordinated nucleotide with 5,6-dimethylbenzimidazole as a base. The upper ligand consists of either 5 ′ -deoxyadenosine (adenosylcobalamin) or a methyl group (methylcobalamin), which functions as the cofactor for methylmalonyl-CoA mutase (MCM, EC 5.4.99.2) and methionine synthase (MS, EC 2.1.1.13), respectively, in mammals ( 1 ).…”

“…Certain bacteria can synthesize B 12 and/or other B 12 -related compounds with a variety of alternative bases (adenine, pseudovitamin B 12 ; 2-methyladenine, Factor A; and so on) in the lower ligand ( 2 , 3 ). We have previously reported that edible cyanobacteria ( Spirulina platensis , Aphanothece sacrum , Aphanizomenon fros-aquae , Nostoc commune , and Nostoc flagelliforme ) contain a substantial amount of pseudovitamin B 12 ( 4 -8 ).…”

“…We have previously reported that edible cyanobacteria ( Spirulina platensis , Aphanothece sacrum , Aphanizomenon fros-aquae , Nostoc commune , and Nostoc flagelliforme ) contain a substantial amount of pseudovitamin B 12 ( 4 -8 ). However, there is little information available on whether these cyanobacteria have the ability to synthesize pseudovitamin B 12 de novo, and whether pseudovitamin B 12 functions as a cofactor for certain cobalamin-dependent enzymes. Although most of these edible cyanobacteria are difficult to use as experimental organisms because of their low growth rates and little biochemical and genomic information, Synechocystis sp.…”