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Isolation and Characterization of Malic Enzyme from Ascaris suum

Description: A procedure for the isolation of malic enzyme from muscle tissue of the roundworm Ascaris suum is described. The fractionation method yields relatively large quantities of the enzyme,with a specific activity of fifteen moles of malate converted to pyruvate and carbon dioxide per min per mg at 25ยบ. Homogeneity was established with analytical ultracentrifugation, zone electrophoresis, isoelectric focusing, and rechromatography. The molecular weight of the enzyme was 250,000, and it is dissociated under several conditions into four identical monomers of 64,000 daltons. The enzyme exists as a single electrophoretic form and prefers manganous and NAD over other cations and NADP. Ammonium sulfate competes with manganous for the active site and titration with DTNB yields eight thiol groups per mole. Titration of the first four thiol groups is accompanied by a complete loss in enzyme activity. Equilibrium dialysis, product inhibition, and initial velocity studies suggest a rapid-equilibrium random sequential mechanism for the Ascaris suum malic enzyme. The presence of 1.3 binding sites per subunits was determined for L-ma late. Antisera prepared against A. suum malic enzyme reacted to a small extent with the NAD malic enzymes from two free-living nematodes, Panarellus redivivus and Turbatrix aceti. A correlation coefficient of 0.911 was obtained upon comparing the amino acid composition of A. suum and E. coli malic enzymes. Some sequence homology is predicted between these malic enzymes. The physiological interpretation favors the binding of malate initially, with the subsequent addition of NAD to the enzyme.
Date: December 1972
Creator: Fodge, Douglas W.
Partner: UNT Libraries

Carbon Dioxide Fixation by Microorganisms

Description: Resting cells of eleven microorganisms were exposed to radioactive carbon dioxide for 40 minutes. The radioactive compounds formed during this time were separated and identified by paper chromatography. Resting cells of Lactobacillus casei fixed no carbon dioxide and growing cells fixed carbon dioxide primarily in malic and aspartic acids. All of the radioactive compounds formed could have become radioactive by reversal of known decarboxylation reactions.
Date: July 24, 1951
Creator: Lynch, Victoria H. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department


Description: The directions for preparing the following acids from labeled acetic acid on a 1 to 20 millimole scale is presented: Succinic acid, malic acid, fumaric acid and tartaric acid. Two methods for preparing the succinic acid are detailed.
Date: June 12, 1951
Creator: Jorgensen, E.C.; Bassham, J.A.; Calvin, M. & Tolbert, B.M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis VIII. The Role of MalicAcid

Description: Malonate has been found to inhibit the formation of malic acid during short periods of photosynthesis with radioactive carbon dioxide. This result, together with studies which show the photosynthetic cycle to be operating normally at the same time, indicates that malic acid is not an intermediate in photosynthesis but is probably closely related to some intermediate of the cycle. Absence of labeled succinic and fumaric acids in these experiments, in addition to the failure of malonate to inhibit photosynthesis, precludes the participation of these acids as intermediates in photosynthesis.
Date: January 25, 1950
Creator: Bassham, James A.; Benson, Andrew A. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis. XVI. Kinetic Relationshipsof the Intermediates in Steady State Photosynthesis

Description: A kinetic study of the accumulation of C{sup 14} in the intermediates of steady state photosynthesis in C{sup 14}O{sub 2} provides information regarding the sequence of reactions involved. The work described applied the radio-chromatographic technique for analysis of the labeled early products. The simultaneous carboxylation reaction resulting in malic acid as well as phosphoglycerate is demonstrated in experiments at high light intensity. A comparison of radioactivities in a number of phosphorylated sugars as a function of time reveals concurrent synthesis of fructose and sedoheptulose phosphates followed by that of ribulose phosphates and later by that of glucose phosphates. The possibility that the cleavage of C{sub 4} compounds to C{sub 2} carbon dioxide acceptors may involve C{sub 7} and C{sub 5} sugars and evidence for this mechanism is presented.
Date: June 5, 1952
Creator: Benson, A.A.; Kawaguchi, S.; Hayes, P. & Calvin, M.
Partner: UNT Libraries Government Documents Department