Demethylthiolating Agents for Ribonucleoside 5′-S-Methyl Phosphorothiolates

Several oxidizing agents were examined for their ability to demethylthiolate adenosine- and cytidine 5′-S-methyl phosphorothiolates.

Iodine dissolved in an aqueous potassium iodide solution or in dimethyl sulfoxide (DMSO) was the most effective demethylthiolating agent of those tested in the present study, rapidly giving the demethylthiolated products in quantitative yields. The iodine-DMSO solution demethyl-thiolated the ribonucleoside 5′-S-methyl phosphorothiolates to give ribonucleoside 5′-monophosphates even under anhydrous conditions, DMSO acting as an oxygen donor in this reaction.

Hydrogen peroxide has high demethylthiolating ability in spite of its low reaction rate. Isoamyl nitrite, an effective demethylthiolating agent for O-alkyl S-methyl phosphorothiolates, was not effective for the demethylthiolation of ribonucleoside 5′-S-methyl phosphorothiolates, because the unprotected amino groups of the S-methyl nucleotides were attacked by the reagent to give deaminated products. N-Chlorosuccinimide had no effect on the demethylthiolation of S-methyl phosphorothiolates.     

Distribution of ω-Amino Acid: Pyruvate Transaminase and Aminobutyrate: α-Ketoglutarate Transaminase in Microorganisms

The distribution of ω-amino acid transaminases in microorganisms was investigated, ω-Amino acid: pyruvate transaminase (ω-APT) was found in bacteria and yeasts, but not in actinomycetes and fungi. On the contrary, aminobutyrate: α-ketoglutarate transaminase (GABA-T) was shown in most of the microorganisms from bacteria to fungi. β-Alanine is a preferred amino donor for the co-APT reaction. Although bacterial and yeast GABA-T are inactive for β-alanine, fungal and actinomycete enzymes react with this compound and γ-aminobutyrate. In comparing these results with those of plant and mammalian enzymes, two different pathways of co-amino acid metabolism are suggested for bacteria, yeast and plants, i.e. one for β-alanine and the other for γ-aminobutyrate, catalyzed by ω-APT and GABA-T, respectively. In actinomycetes, fungi, and mammals GABA-T may be involved in the metabolism of both ω-amino acids. In addition, evolutionary changes of ω-amino acid transaminases are discussed.     

Post-translational Modification of κ-Casein in the Golgi Apparatus of Mid-lactating Mammary Glands from Rat and Cow

Bovine κ-casein, a phosphoglycoprotein, has mucin-type carbohydrate chains. Subcellular distribution of enzymes that take part in the post-translational modification of κ-casein was examined. In lactating mammary glands from rats and cows, N-acetyl-galactosaminyl transferase, galactosyl transferase, sialyl transferase, and casein kinase were localized specifically in the Golgi apparatus.

The substrate specificities indicate that these enzymes are actually responsible for the processing of κ-casein.

The presence of a phosphate group attached to κ-casein did not affect the rate of glycosylation by N-acetyl-galactosaminyl transferase, while the presence of carbohydrate chains attached to κ- casein strongly reduced the rate of phosphorylation by casein kinase. These results suggest that in the Golgi apparatus, phosphorylation of κ-casein precedes glycosylation.     

Lipids of Streptomyces sioyaensis

Lipids were extracted with chloroform-methanol from Streptomyces sioyaensis and fractionated on a silicic acid column. Lipids of Streptomyces sioyaensis were mainly composed of neutral lipids, cardiolipin, phosphatidylethanolamines, phosphatidylinositolmonomanno- side and a new lysine-containing lipid.     

Role of O-Methyltransferase in the Lignification of Bamboo

Characterization of S-adenosylmethionine: catechol O-methyltransferase (EC. 2. 1. 1.6) isolated from bamboo shoot was carried out. Ferulic and sinapic acids which are believed to be lignin precursors are formed by the mediation of the enzyme, and the enzyme activity increased progressively during the lignification of bamboo shoots. Evidences suggest that this enzyme may contribute to the synthesis of lignin precursors.     

l-Glutamic Acid Fermentation

A study was made on the differences between Brevibacterium thiogenitalis No. 653 and its oleic acid-requiring mutant D-248 in some physiological characteristics.

The most important difference of the characteristics was found in their intracellular fatty acid contents. Namely, the cellular oleic acid content of D-248 was scarcely affected by biotin but limited by the oleic acid which was added to the medium.

On the other hand, various enzyme activities and rates of oxygen uptake for several organic acids were found to be slightly different between the two strains.

These observations suggest that oleic acid has an important role for the production of l-glutamic acid.

The effect of biotin and oleic acid on the cellular fatty acid contents, and the relation between the cellular fatty acid contents and the productivity of l-glutamic acid were investigated using Brevibacterium thiogenitalis No. 653 and its oleic acid-requiring mutant, D-248.

While the synthesis of palmitic acid in D-248 was stimulated by biotin and competitively reversed by oleic acid added to the culture medium, the level of cellular oleic acid was scarcely affected by biotin but regulated by oleic acid in the medium.

For the productivity of L-glutamic acid, the most important factor was the level of cellular oleic acid, and the effect of cellular palmitic acid was considerably weak. This relation was subjected to a figuration and able to be expressed on the whole as one exponential-like curve. An amount of over 70 per cent of cellular fatty acids was distributed in the phospholipid fraction and its fatty acid composition was almost the same as that of whole cells.     

Metabolism of Thiophene-2-carboxylate by a Photosynthetic Bacterium

A photosynthetic bacterium, which can grow photosynthetically on benzoate, was isolated from sewage mud. Various kinds of aromatic compounds including heterocyclic aromatic compounds were photometabolized by the washed cells grown photosynthetically on benzoate with no lag period. Among these, thiophene-2-carboxylate was metabolized most rapidly to its (+)-tetrahydro derivative. The same strain could also grow on succinate under photosynthetic conditions. However, thiophene-2-carboxylate was only photometabolized after a long lag period by the washed cells grown photosynthetically on succinate, and the metabolite was not its (+)-tetrahydro derivative but (+)-3-hydroxytetrahydrothiophene-2-carboxylate. In the presence of chloramphenicol, an inhibitor of protein synthesis, the photometabolism of thiophene-2-carboxylate by the washed cells grown photosynthetically on benzoate was not affected at all, but the photometabolism of the same substrate by the washed cells grown photosynthetically on succinate was completely inhibited. These results indicate that a reduction system of broad substrate specificity for aromatic rings is already present in the benzoate-grown cells but absent in the succinate-grown cells. It seems that such a reduction system for aromatic rings is induced by an aromatic substrate.     

Studies on Lactic Acid Fermentation

Resting cells of l. fermentum convert glyceraldehyde to equimolar lactic acid and neither the evolution of carbon dioxide nor the uptake of oxygen was observed. Glyceraldehyde-3-phosphate and 3-phosphoglycerate were identified as intermediates which were equally labeled with inorganic P³² in reaction systems, and the presence of triokinase was suggested.