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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.
L U Tan, and
E J Drury, and
R E MacKenzie
January 1980,
Methods in enzymology,
L U Tan, and
E J Drury, and
R E MacKenzie
November 1977,
Biochimica et biophysica acta,
L U Tan, and
E J Drury, and
R E MacKenzie
November 1983,
Canadian journal of biochemistry and cell biology = Revue canadienne de biochimie et biologie cellulaire,
L U Tan, and
E J Drury, and
R E MacKenzie
February 1978,
Biochimica et biophysica acta,
L U Tan, and
E J Drury, and
R E MacKenzie
June 1979,
Canadian journal of biochemistry,
L U Tan, and
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R E MacKenzie
January 2008,
Vitamins and hormones,
L U Tan, and
E J Drury, and
R E MacKenzie
November 1985,
Canadian journal of biochemistry and cell biology = Revue canadienne de biochimie et biologie cellulaire,
L U Tan, and
E J Drury, and
R E MacKenzie
June 1989,
American journal of human genetics,
L U Tan, and
E J Drury, and
R E MacKenzie
April 1992,
The Journal of biological chemistry,
L U Tan, and
E J Drury, and
R E MacKenzie
November 1988,
The Journal of biological chemistry,
