title: Methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase-formyltetrahydrofolate synthetase. A multifunctional protein from porcine liver.
abstract: Methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase, and formyltetrahydrofolate synthetase from porcine liver have been co-purified more than 500-fold to apparent homogeneity. The inability of three sequential chromatographic procedures followed by affinity chromatography using NADP+- or ATP-substituted Sepharose to resolve the three activities demonstrates that they are physically associated. Molecular weight estimates of the native protein by gel filtration (Mr = 150,000) and by dodecyl sulfate gel electrophoresis (Mr = 100,000) indicate that the native structure is probably a single subunit. Since only one protein band is seen on dodecyl sulfate gels, it is concluded that the three activities are properties of a single polypeptide chain. The kinetic properties of the three activities are described, the most unusual feature being the susceptibility of the cyclohydrolase to competitive inhibition by NADP+, NAD+, ATP, and folate.
mesh_terms: D000619:Aminohydrolases / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D005574:Formate-Tetrahydrofolate Ligase / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008025:Ligases / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D013552:Swine; D013763:Tetrahydrofolates
chemical_list: D009097:Multienzyme Complexes; D013763:Tetrahydrofolates; D010088:Oxidoreductases; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D000619:Aminohydrolases; D008025:Ligases; D005574:Formate-Tetrahydrofolate Ligase