scholarly journals Incorporation of dl-[2−14C]ornithine and dl-[5−14C]arginine in milk constituents by the isolated lactating sheep udder

1968 ◽  
Vol 106 (3) ◽  
pp. 719-724 ◽  
Author(s):  
R. Verbeke ◽  
G. Peeters ◽  
Anne Marie Massart-Leën ◽  
G. Cocquyt
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Glutamic Acid ◽  
Mammary Glands ◽  
Total Radioactivity ◽  
Chemical Degradation ◽  
Mammary Tissue ◽  
Specific Activities ◽  
Plasma Arginine

1. Lactating mammary glands of sheep were perfused for several hours in the presence of dl-[2−14C]ornithine or dl-[5−14C]arginine and received adequate quantities of acetate, glucose and amino acids. 2. In the [14C]ornithine experiment 1·4% of the casein and 1% of the expired carbon dioxide came from added ornithine; 96% of the total radioactivity in casein was recovered in proline; 13% of the proline of casein originated from plasma ornithine. 3. In this experiment the results of chemical degradation of proline of casein as well as relative specific activities in the isolated products are consistent with the view that ornithine is metabolized, by way of glutamic γ-semialdehyde, to proline or glutamic acid. 4. In the [14C]arginine experiments 3% of the casein and 1% of the expired carbon dioxide came from arginine; 84% of the arginine and 9% of the proline of casein originated from plasma arginine. 5. In these experiments the relative specific activities of arginine, ornithine and proline in plasma are in agreement with the view that arginine is metabolized by way of ornithine to proline. The conversion of arginine into ornithine is probably catalysed by arginase, so that arginase in mammary tissue may be involved in the process of milk synthesis.

Metabolism of [U-14C; 2, 3-3H]-L-valine by the isolated perfused goat udder

1979 ◽  
Vol 46 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Eddy Roets ◽  
Anne-Marie Massart-LeëN ◽  
Roger Verbeke ◽  
Georges Peeters
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Citric Acid ◽  
Glutamic Acid ◽  
Milk Fat ◽  
Mammary Glands ◽  
Mammary Tissue ◽  
Total Milk ◽  
Important Amount ◽  
Free Plasma

SUMMARYTwo lactating mammary glands excised from 2 goats were perfused for several hours in the presence of [U-14C; 2,3-3H]-L-valine and received adequate quantities of glucose, acetate and amino acids. In the synthesized milk 96 and 89% respectively of the casein valine was derived from free plasma valine. Valine was extensively catabolized by mammary tissue, resulting in a considerable 14CO2 production and in the incorporation of 14C into milk citric acid and to a lesser extent into casein aspartic acid and glutamic acid. About 30% of the valine molecules which were taken up by the mammary gland were oxidized to CO2 and 70% were incorporated in casein as valine residues. About 10% of the plasma valine molecules were reversibly transaminated during one passage through the udder. An important amount of radioactivity of plasma was present in unknown metabolites. Only 7% of this activity was localized in isobutyrate. The radioactivity of total milk fat was very low. Mainly iso-14:0, iso-16:0 and 15:0 were labelled.

Metabolism of [U-14C]-l-threonine and [U-14C]-l-phenylalanine by the isolated perfused udder

1972 ◽  
Vol 39 (2) ◽  
pp. 239-250 ◽  
Author(s):  
R. Verbeke ◽  
E. Roets ◽  
Anne-Marie Massart-Leën ◽  
G. Peeters
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Citric Acid ◽  
Glutamic Acid ◽  
Plasma Levels ◽  
Mammary Tissue ◽  
Phenylalanine Concentration ◽  
Plasma Phenylalanine ◽  
Lactating Mammary Gland ◽  
Specific Activities

SummaryA lactating mammary gland of a goat was perfused for 9 h in the presence of [U-14C]-l-threonine and received adequate quantities of glucose, acetate and amino acids. Two lactating sheep udders were likewise perfused in the presence of [U-14C]-l-phenylalanine: the plasma levels of phenylalanine in the first of these experiments were 4 times higher than in the second.In the [14C]threonine experiment, 4 % of the casein and 0·4 % of the expired CO2 were derived from threonine; 85 % of the threonine and 1·6 % of the glycine residues in casein originated from plasma threonine. Small 14C levels were found in glutamic acid, aspartic acid and serine of casein. The relative specific activities amongst the casein amino acids and the appearance of appreciable labelling in plasma glycine are consistent with the view that threonine is split by threonine aldolase.In the [14C]phenylalanine experiments virtually no radioactivity was detected in CO2, lactose or citric acid, indicating that this substrate is not broken down by mammary tissue. In the second experiment, 96 % of the phenylalanine and 0·3 % of the tyrosine of casein originated from plasma phenylalanine. In the first experiment, a 30-fold higher 14C incorporation into casein tyrosine relative to phenylalanine was observed. The possible significance of the phenylalanine concentration in the plasma on the degree of conversion of phenylalanine into tyrosine within the mammary gland is discussed.

STUDIES ON WHEAT PLANTS USING CARBON-14 COMPOUNDS: XXI. THE METABOLISM OF GLYCINE-2-C14

1964 ◽  
Vol 42 (9) ◽  
pp. 1293-1299 ◽  
Author(s):  
W. B. McConnell
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Glutamic Acid ◽  
Specific Activity ◽  
Total Carbon ◽  
Gluten Protein ◽  
Carbon 14 ◽  
Specific Activities

Glycine-2-C14was administered to 83-day-old wheat plants. The plants were allowed to mature fully and the carbon-14 distribution was then examined. About 80% of the radioactivity injected was recovered in the upper portions of the plant, the kernels themselves containing 66%. Proteins had a higher specific activity than other kernel constituents but the starch contained about one-half the total carbon-14 of the kernels. Glycine and serine were by far the most radioactive amino acids of the gluten protein. They had specific activities of 2720 and 2900 μc/mole C respectively while alanine, histidine, methionine, glutamic acid, and proline had specific activities ranging from 150 to 300 μc/mole C. The specific activities of carbons 1 and 2 of glycine recovered from the protein were 550 and 4900 μc/mole respectively while the specific activities of carbons 1, 2, and 3 of serine were 490, 4300, and 3100 μc/mole respectively. The results confirm previous views regarding extensive interconversion of glycine and serine in maturing wheat. Extensive labelling in carbon 3 of serine is interpreted as evidence that glycine is degraded to "active formaldehyde" and carbon dioxide.

THE METABOLISM OF PROPIONATE BY WHEAT STEM RUST UREDOSPORES

1963 ◽  
Vol 41 (3) ◽  
pp. 737-743 ◽  
Author(s):  
H. Reisener ◽  
A. J. Finlayson ◽  
W. B. McConnell ◽  
G. A. Ledingham
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Glutamic Acid ◽  
Stem Rust ◽  
Water Extract ◽  
Hot Water ◽  
Insoluble Residue ◽  
Soluble Carbohydrates ◽  
Wheat Stem Rust ◽  
Carbon 14

When uredospores of wheat stem rust were shaken for 3 hours with phosphate buffer (pH 6.2) containing propionate-1-C14, -2-C14, or -3-C14, about 55% of the carbon-14 was removed from the solution. With propionate-1-C14, most of the carbon-14 taken up was released as carbon dioxide-C14, whereas about 20% and 31% of propionate carbon 2 and carbon 3, respectively, was incorporated into the spores. The specific activity of a fraction consisting of the free amino acids of a hot-alcohol and hot-water extract of the spores increased markedly with increase in the position number of propionate in which the carbon-14 was located. A similar relation was observed for other fractions such as soluble carbohydrates, ether-soluble material, organic acids, and insoluble residue from spores. The most active amino acids isolated were glutamic acid, γ-aminobutyric acid, and alanine. Partial degradations showed that with propionate-2-C14 the carboxyl groups of glutamic acid were especially radioactive, whereas with propionate-3-C14 the internal carbons were most radioactive.It is concluded that propionate metabolism in the rust spores involved conversion of carbon 1 to carbon dioxide, and utilization of carbons 2 and 3 as acetate with carbon 2 behaving as the carboxyl carbon.

PYOCYANINE FORMATION FROM LABELLED SUBSTRATES BY PSEUDOMONAS AERUGINOSA

1957 ◽  
Vol 3 (2) ◽  
pp. 165-169 ◽  
Author(s):  
A. C. Blackwood ◽  
A. C. Neish
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Pseudomonas Aeruginosa ◽  
Calcium Carbonate ◽  
Specific Activity ◽  
The Other ◽  
Specific Activities ◽  
Carbonate Salts ◽  
Cell Carbon

Pseudomonas aeruginosa was grown under conditions suitable for pyocyanine production in a medium containing glycerol, L-leucine, DL-alanine, calcium carbonate, salts, and small amounts of various C14-labelled substrates. A comparison of the specific activities of the cell carbon, respiratory carbon dioxide, and pyocyanine carbon showed that glycerol and dihydroxyacetone were the only substrates from which pyocyanine having a specific activity higher than the cell carbon was formed. Glucose, fructose, pyruvate, acetate, and the 13 amino acids tested were inferior in this respect. Alanine, leucine, isoleucine, and glycine were incorporated into pyocyanine more readily than the other amino acids. Phenylalanine and tyrosine, although possessing preformed rings, were poor precursors of pyocyanine and were oxidized more readily than they were assimilated. These results suggest that pyocyanine originates from trioses but gives little indication of the nature of the intermediates.

SOURCES OF CARBON FOR THE SYNTHESIS OF PROTEIN AMINO ACIDS IN ATTACHED PHOTOSYNTHESIZING WHEAT LEAVES

1963 ◽  
Vol 41 (7) ◽  
pp. 985-994 ◽  
Author(s):  
J. A. Hellebust ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Protein Turnover ◽  
Soluble Sugars ◽  
Protein Nitrogen ◽  
Considerable Portion ◽  
Protein Amino Acids ◽  
Specific Activities ◽  
Wheat Leaves

Attached, rapidly growing wheat leaves were allowed to photoassimilate C14O2 and C12O2 alternately. Samples of leaves were collected after each period of photosynthesis and were analyzed for amounts and total activities of soluble sugars and amino acids, and protein amino acids. The leaves were also analyzed for protein nitrogen and amounts and total activities of respired carbon. Samples of roots were also collected and the amounts, total activities, and specific activities of their soluble compounds were determined. It was possible to calculate from these data the proportions of carbon entering some protein amino acids which came either from soluble amino acid pools or by a direct route from photosynthate, bypassing the soluble pools. More than half of the carbon entering protein-bound serine and glycine was derived from newly assimilated CO2, while protein glutamic acid, aspartic acid, and alanine derived more of their carbon from the soluble amino acid pools. Analysis of the data from roots indicated that a considerable portion of the carbon translocated from the leaves was derived from newly assimilated CO2. There was some indication that protein turnover took place, but it was concluded that proteins could not have contributed significantly as substrates for respiration in these leaves.

UTILIZATION OF ADDED SUBSTRATES BY UREDOSPORES OF WHEAT STEM RUST

1956 ◽  
Vol 2 (6) ◽  
pp. 559-563 ◽  
Author(s):  
P. Shu ◽  
A. C. Neish ◽  
G. A. Ledingham
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Fatty Acids ◽  
Glutamic Acid ◽  
Metabolic Activity ◽  
Stem Rust ◽  
Volatile Fatty Acids ◽  
The Other ◽  
Wheat Stem Rust ◽  
Better Than

Uredospores of wheat stem rust utilized a number of externally-supplied, labelled carbohydrates, amino acids, and volatile fatty acids. The carbon of these substrates appeared in the spore materials and in the carbon dioxide. This metabolic activity, though very weak, is definite. D-Mannose, D-mannitol, D-glucose, sucrose, and D-fructose were utilized better than the other carbohydrates. Glutamic acid gave the highest yield of carbon dioxide while the basic amino acids, L-arginine and L-lysine, were more efficiently incorporated into the spore material.

The metabolism of 14C-urea by white spruce seedlings in light and darkness

1973 ◽  
Vol 51 (6) ◽  
pp. 1197-1211 ◽  
Author(s):  
D. J. Durzan
Keyword(s):  
Carbon Dioxide ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Urease Activity ◽  
De Novo ◽  
White Spruce ◽  
Acid Synthesis ◽  
Transfer Rna ◽  
Ammonium Ions ◽  
Specific Activities

Weak urease activity was detected in 2-week-old white spruce seedlings. The addition of urea to these seedlings increased urease activity in light compared to darkness. Urease was localized in the cytoplasm mainly in the epidermal cells, and to a lesser extent in vascular tissues and at the shoot apex.In light, the early products of 14C-urea indicated the release of 14C-carbon dioxide and ammonium ions. Radioactivity appeared in the anionic and neutral fractions and then in alanine, serine, and glycine, just as in the fixation of 14C-bicarbonate. By 4 h most radioactivity resided in glutamic acid and alanine. This pattern was associated with increased protein synthesis, and with high levels of free glutamine. Serine, glycine, alanine, and carbamyl aspartic acid had high specific activities.In darkness, radioactivity in alanine persisted, but levels in serine, glycine, and protein were low. Most radioactivity eventually resided in asparagine. Radioactive urea and citrulline were kept at higher levels than in light. Glutamic acid, citrulline, and carbamyl aspartic acid had the greatest specific activities. In light and darkness, carbamyl derivatives were formed more readily from 14C-urea than from 14C-bicarbonate.Carbamyl phosphate was implicated as a precursor of citrulline and arginine as well as for carbamyl aspartic acid. In light, radioactivity was recovered from ribosomal (25, 23, 18, 16, and 5 S) and transfer RNA (4 S). This resided mainly in uracil and cytosine. By contrast, in DNA, radioactivity was recovered mainly from thymine, cytosine, and 5-methylcytosine. In rapidly growing seedlings, urea contributed to de novo nucleic acid synthesis mainly through pyrimidine pathways via carbamyl aspartic acid.

THE METABOLISM OF PROPIONATE BY WHEAT STEM RUST UREDOSPORES

1963 ◽  
Vol 41 (1) ◽  
pp. 737-743 ◽  
Author(s):  
H. Reisener ◽  
A. J. Finlayson ◽  
W. B. McConnell ◽  
G. A. Ledingham
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Glutamic Acid ◽  
Stem Rust ◽  
Water Extract ◽  
Hot Water ◽  
Insoluble Residue ◽  
Soluble Carbohydrates ◽  
Wheat Stem Rust ◽  
Carbon 14

When uredospores of wheat stem rust were shaken for 3 hours with phosphate buffer (pH 6.2) containing propionate-1-C14, -2-C14, or -3-C14, about 55% of the carbon-14 was removed from the solution. With propionate-1-C14, most of the carbon-14 taken up was released as carbon dioxide-C14, whereas about 20% and 31% of propionate carbon 2 and carbon 3, respectively, was incorporated into the spores. The specific activity of a fraction consisting of the free amino acids of a hot-alcohol and hot-water extract of the spores increased markedly with increase in the position number of propionate in which the carbon-14 was located. A similar relation was observed for other fractions such as soluble carbohydrates, ether-soluble material, organic acids, and insoluble residue from spores. The most active amino acids isolated were glutamic acid, γ-aminobutyric acid, and alanine. Partial degradations showed that with propionate-2-C14 the carboxyl groups of glutamic acid were especially radioactive, whereas with propionate-3-C14 the internal carbons were most radioactive.It is concluded that propionate metabolism in the rust spores involved conversion of carbon 1 to carbon dioxide, and utilization of carbons 2 and 3 as acetate with carbon 2 behaving as the carboxyl carbon.

Metabolism of [U-14C]D-fructose by the isolated perfused udder

1969 ◽  
Vol 36 (2) ◽  
pp. 233-239 ◽  
Author(s):  
R. Verbeke ◽  
Anne-Marie Massart-Leën ◽  
G. Peeters
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Citric Acid ◽  
Glutamic Acid ◽  
Krebs Cycle ◽  
Casein Hydrolysate ◽  
Relative Distribution ◽  
Limited Extent ◽  
Lactating Mammary Gland ◽  
Specific Activities

SummaryA lactating mammary gland of a sheep and a goat were perfused for several hours in the presence of [U-14C]D-fructose and received adequate quantities of acetate, glucose and amino acids.In both experiments, there was a small incorporation of 14C in the expired CO2. Smaller radioactivities were measured in milk citric acid, lactose, casein and fat, the activities decreasing in that order. The specific activities of the amino acids from one casein hydrolysate were determined. The highest radioactivities were found in alanine and serine; methionine, glutamic acid and aspartic acid showed a smaller incorporation of 14C.These results indicate that fructose is metabolized only to a very limited extent by the mammary gland. The relative distribution of 14C observed among the different substances isolated may be explained by a direct splitting of fructose into two C3-fragments, glycolysis and metabolism via the Krebs cycle.

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