83] Methylenetetrahydrofolate dehydrogenase from Clostridium formicoaceticum and methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase (combined) from Clostridium thermoaceticum

Abstract

Publisher Summary This chapter discusses methylenetetrahydrofolate dehydrogenase from Clostridium formicoaceticum and methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase (combined), from Clostridium thermoaceticum. Methylenetetrahydrofolate dehydrogenase is widely distributed and has been found in every cell type investigated. The nicotinamide adenine dinucleotide (NAD)-specific enzyme has been purified to homogeneity from Clostridium formicoaceticum, and the nicotinamide adenine dinucleotide phosphate (NADP)-specific enzyme has been obtained from Clostridium thermoaceticum. Other sources of the NADP-specific enzyme are Streptococcus species, Escherichia coli, Clostridium cylindrosporum, Salmonella typhimurium, yeast, liver from various animals, calf thymus, and plants. The NAD-specific enzyme has been demonstrated in Acetobacterium woodii, some methane bacteria, and in Ehrlich ascites tumor cells. Of considerable interest are the observations in porcine and ovine livers, as well as in yeast, methylenetetrahydrofolate dehydrogenase purified to homogeneity also contains methylenetetrahydrofolate cyclohydrolase and formyltetrahydrofolate synthetase activities. Many properties of methylenetetrahydrofolate dehydrogenase from C. formicoaceticum and of methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase (combined) from C. thermoaceticum are discussed in the chapter. The physical properties of the two enzymes are almost identical. Both have molecular weights around 60,000 and consist of two subunits that are of identical molecular weight in the respective enzymes.