EurekaMag.com logo
+ Site Statistics
References:
53,623,987
Abstracts:
29,492,080
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on LinkedInFollow on LinkedIn

+ Translate

Methylene tetra hydro folate reductase steady state and rapid reaction studies on the nadph methylene tetra hydro folate nadph menadione and methyl tetra hydro folate menadione oxido reductase activities of the enzyme



Methylene tetra hydro folate reductase steady state and rapid reaction studies on the nadph methylene tetra hydro folate nadph menadione and methyl tetra hydro folate menadione oxido reductase activities of the enzyme



Journal of Biological Chemistry 258(19): 11510-11514



Methylenetetrahydrofolate reductase is a flavoprotein which was recently purified to homogeneity from pig liver. The enzyme catalyzes the transfer of reducing equivalents from NADPH to menadione or methylenetetrahydrofolate, or from methyltetrahydrofolate to menadione. The individual reductive and oxidative half-reactions comprising these activities were examined, measuring the rate of flavin reduction or oxidation in an anaerobic stopped flow apparatus. In all cases, the individual half-reactions occur at rates which are sufficiently fast to account for catalytic turnover, indicating that the enzyme is kinetically competent to catalyze these oxidoreductions by Ping Pong Bi Bi mechanisms. NADPH-linked reduction of the flavin appears to be rate-limiting for the NADPH-menadione oxidoreductase reaction, while reoxidation of the flavin is partially rate-limiting for the NADPH-methylenetetrahydrofolate oxidoreductase reaction. Reduction of the flavin by methyltetrahydrofolate is rate-limiting in the methyltetrahydrofolate-menadione oxidoreductase reaction. No intermediates are seen in any of these half-reactions. In agreement with the postulate of ping-pong mechanisms for the catalytic reactions of the enzyme is the observation of exchange of radiolabel between [methyl-14C]methyltetrahydrofolate and [methylene-14C]methylenetetrahydrofolate in the absence of either menadione or pyridine nucleotides. The rate of exchange when both substrates are saturating is in good agreement with the rate of the methyltetrahydrofolate-menadione oxidoreductase reaction measured under Vmax conditions.

(PDF 0-2 workdays service: $29.90)

Accession: 005892062

Download citation: RISBibTeXText



Related references

Studies on the regulation of 1 carbon metabolism the effects of folate concentration in the growth medium on the activity of 3 folate dependent enzymes in lactobacillus casei enz 10 formyl tetra hydro folate synthetase enz di hydro folate reductase enz 5 10 methylene tetra hydro folate dehydrogenase. Journal of Biological Chemistry 244(8): 1988-1993, 1969

Effect of nitrous oxide induced inactivation of vitamin b 12 on the activity of formylmethenylmethylene tetra hydro folate synthetase methylene tetra hydro folate reductase and formimino tetra hydro folate transferase. Biochemical & Biophysical Research Communications 97(4): 1329-1333, 1980

Methylene tetra hydro folate reductase in cultured human cells part 2 genetic and biochemical studies of methylene tetra hydro folate reductase deficiency. Pediatric Research 11(11): 1141-1143, 1977

Methylene tetra hydro folate dehydrogenase ec 1.5.1.5 methenyl tetra hydro folate cyclo hydrolase ec 3.5.4.9 formyl tetra hydro folate synthetase ec 6.3.4.3 from porcine liver location of the activities in 2 domains of the multi functional poly peptide. Canadian Journal of Biochemistry 57(6): 806-812, 1979

Methylene tetra hydro folate dehydrogenase ec 1.5.1.5 and methylene tetra hydro folate reductase ec 1.1.1.68 activity in normal and brugia pahangi infected aedes aegypti. Journal of Parasitology 64(4): 661-668, 1978

A complex of n 5 n 10 methylene tetra hydro folate dehydrogenase ec 1.5.1.5 and n 5 n 10 methenyl tetra hydro folate cyclo hydrolase in escherichia coli purification subunit structure and allo steric inhibition by n 10 formyl tetra hydro folate. Journal of Biological Chemistry 253(12): 4245-4253, 1978

Co purification and properties of n 10 formyl tetra hydro folate synthetase methenyl tetra hydro folate cyclo hydrolase and methylene tetra hydro folate dehydrogenase derived from human chronic lymphocytic leukemic blast cells. Federation Proceedings 37(3): 493, 1978

Penta glutamate derivatives of folate as substrates for rat liver tetra hydro pteroyl glutamate methyl transferase ec 21113 and 5 10 methylene tetra hydro folate reductase ec 11168. 1975

Methylene tetra hydro folate dehydrogenase ec 1.5.1.5 methenyl tetra hydro folate cyclo hydrolase ec 3.5.4.9 formyl tetra hydro folate synthetase ec 6.3.4.3 from porcine liver interaction between the dehydrogenase and cyclo hydrolase activities of the multi functional enzyme. Biochimica et Biophysica Acta 522(2): 311-317, 1978

An eukaryotic protein synthesizing 10 formyl tetra hydro folate 5 10 methyenyl tetra hydro folate and 5 10 methylene tetra hydro folate. Federation Proceedings: 837, 1976

Methylene tetra hydro folate dehydrogenase ec 1.5.1.5 methenyl tetra hydro folate cyclo hydrolase ec 3.5.4.9 and formyl tetra hydro folate synthetase ec 6.3.4.3 from porcine liver isolation of a dehydrogenase cyclo hydrolase fragment from the multi functional enzyme. Biochimica et Biophysica Acta 485(1): 52-59, 1977

Synthesis of deuterium labeled 6 r 11 s and 6 r 11 r 5 10 methylene tetra hydro folate stereochemical paths of serine hydroxymethyl transferase ec 2.1.2.1 5 10 methylene tetra hydro folate dehydrogenase ec 1.5.1.5 and thymidylate synthetase ec 2.1.1.b catalysis/. Journal of the American Chemical Society 106(6): 1833-1838, 1984

Inhibition of pig liver methylene tetra hydro folate reductase ec 1.1.99.15 by di hydro folate some mechanistic and regulatory implications. Biochemistry 18(22): 4845-4851, 1979

Modulation of methylene tetra hydro folate reductase ec 119915 activity by s adenosyl methionine and di hydro folate and its poly glutamate analogs. 1982