The Synthesis of Amino Acids by Organized Enzyme Systems

Wagner, Robert P.; Bergquist, Arloa; Brotzman, B.; Eakin, E.; Clarke, Charles Hugh; Page, R.

doi:10.1016/b978-0-12-395658-3.50030-7

Cited by 7 publications

(2 citation statements)

References 30 publications

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“…Enzymatic properties of partially purified agarose I AAS. In order to demonstrate the enzymatic reaction products, AAS purified 34fold on an agarose column was incubated with pyruvate and a-ketobutyrate for 4 hr at 35 C. Pteridine derivatives of the carbinols of the enzymatically synthesized acetolactate and acetohydroxy butyrate were prepared according to the procedures of Wagner, Bergquist, and Forrest (29). The RF values of the derivatives were averaged from two different chromatograms and compared to standards made from the carbinols of synthetically prepared acetolactate and acetohydroxy butyrate.…”

Section: Downloaded Frommentioning

confidence: 99%

Acetohydroxy Acid Synthetase with a p H Optimum of 7.5 from Neurospora crassa Mitochondria: Characterization and Partial Purification

1972

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Section: Downloaded Frommentioning

confidence: 99%

Acetohydroxy Acid Synthetase with a p H Optimum of 7.5 from Neurospora crassa Mitochondria: Characterization and Partial Purification

1972

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“…It has been previously speculated (21) that the four enzymes in the biosynthetic pathway from pyruvate may reside inside the mitochondrion as an organized multienzyme complex . While our data neither completely confirm nor negate this speculation, the demonstration in vitro that the individual activities of each of the enzymes, when solubilized into the S 1 , or light sucrose fraction of a discontinuous gradient, retain the ability to catalyze valine synthesis from pyruvate, emphasizes that a loose association of the four enzymes is sufficient for valine synthesis .…”

Section: Discussionmentioning

confidence: 99%

SEPARATION OF MITOCHONDRIAL MEMBRANES OF NEUROSPORA CRASSA

Cassady

Leiter

Bergquist

et al. 1972

The Journal of Cell Biology

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Separation of Neurospora mitochondrial outer membranes from the inner membrane/matrix fraction was effected by digitonin treatment and discontinuous density gradient centrifugation. The solubilization of four isoleucine-valine biosynthetic enzymes was studied as a function of digitonin concentration and time of incubation in the detergent. The kinetics of the appearance of valine biosynthetic function in fractions outside of the inner membrane/matrix fraction, coupled with enzyme solubilization patterns similar to that for the matrix marker, mitochondrial malate dehydrogenase, indicate that the four isoleucine-valine pathway enzymes are localized in the mitochondrial matrix.

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Heart induction in salamanders

Jacobson

Duncan

1968

J. Exp. Zool.

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Heart determination is a gradual, cumulative process involving inductive and suppressive interactions between the heart mesoderm and nearby embryonic tissues. Our analysis of heart determination in the California newt, Taricha torosa, includes defect and other i n vivo experiments, and explants in epidermal vesicles and into hanging drops.Explants of presumptive heart mesoderm from neurulae into hanging drops of a completely defined salt solution (Niu-Twitty solution) produce beating hearts only infrequently. The addition of various other tissues and fractions of tissue homogenates changes the frequency and the rate of differentiation. These two parameters were used to assess the stimulatory and suppressive effects of tissues and tissue fractions on the differentiation of the presumptive heart mesoderm.At least three different factors are active in eliciting and regulating heart differentiation. A specific heart inductor in anterior endoderm increases the rate and the frequency of heart differentiation. A general stimulatory factor in epidermis and other embryonic tissues increases the frequency, but not the rate, of heart differentiation. A n inhibitory agent in cranial fold and neural plate tissues delays or prevents heart differentiation. These three factors operate from intact tissues in the embryo or when explanted in vesicles or hanging drops, and are effectively present in a fraction (from sephadex column chromatography) of homogenates of the appropriate tissues.Heart formation in vertebrates is clearly dependent upon a variety of developmental conditions and processes. We shall describe some of these and attempt to integrate them into a unified concept of heart differentiation.By the time an embryo has formed the three germ layers, heart potentialities have become limited to, or have developed only in, specific regions of the mesoderm. Portions of the endoderm and the ectoderm have significant interactions with the mesoderm, and these interactions control heart formation. As with so many organs, the heart is induced.Prospective heart mesoderm has its most important inductive interactions with the anterior dorso-lateral endoderm of the early embryo. This has been experimentally demonstrated in amphibians (Mangold, '56; Chuang and Tseng, '57; Amano, '58; Jacobson, '60, '61), in chicks (Orts-Llorca, '63; Orts-Llorca and Gil, '65), and is implied for human embryos by observations of Hommes ('57).Partly as a result of embryonic induction, areas of mesoderm become determined to form a whole heart. For a time during heart determination, any part of such an area may form a whole heart if isolated from the remainder. This is readily seen if one prevents the fusion of the two groups that normally come together to form a single heart. Each half-rudiment forms a whole heart, one the mirror image of the other (Ekman, '25; Copenhaver, '26, '55; DeHaan, '65).The positions of the cells that are induced to form heart and the morphogenetic movements that bring these cells to the heart site need explanation. Atte...

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The Synthesis of Amino Acids by Organized Enzyme Systems

Cited by 7 publications

References 30 publications

Acetohydroxy Acid Synthetase with a p H Optimum of 7.5 from Neurospora crassa Mitochondria: Characterization and Partial Purification

Acetohydroxy Acid Synthetase with a p H Optimum of 7.5 from Neurospora crassa Mitochondria: Characterization and Partial Purification

SEPARATION OF MITOCHONDRIAL MEMBRANES OF NEUROSPORA CRASSA

Heart induction in salamanders

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