Richard U. Byerrum

Two Isoforms of Dihydroxyacetone Phosphate Reductase from the Chloroplasts of Dunaliella tertiolecta

Three isoforms of dihydroxyacetone phosphate reductase in extracts from Dunaliella tertiolecta have been separated by a diethylaminoethyl cellulose column chromatography with a shallow NaCl gradient. The chloroplasts contained the two major isoforms, and the third, minor form was in the cytosol. The isoforms are unstable in the absence of glycerol and they are cold labile, but they may be partially reactivated at 35[deg]C. The first chloroplast form to elute from the DEAE cellulose column was the major form when the cells were grown on high NaCl and it has been referred to as the form for glycerol production for osmoregulation or “osmoregulator form.” The second form increased in specific activity when inorganic phosphate was increased in the growth media to stimulate growth, and it has been given the designation for the form for glyceride synthesis, “glyceride form.” The osmoregulator form was stimulated by NaCl added to the enzyme assay, but not by reduced Escherichia coli thioredoxin. The glyceride form had properties similar to the enzyme in leaf chloroplast, such as inhibition by NaCl and by fatty acyl-coenzyme A derivatives and some stimulation by dithiothreitol, uridine diphosphate galactose, cyti-dine diphosphate dipalmatoyl diglyceride, and reduced E. coli thioredoxin. Thus, Dunaliella chloroplasts have a salt-stimulated osmoregulatory form of dihydroxyacetone phosphate reductase, which seems to have a role in glycerol production, and an isoform, which may be involved in glyceride synthesis and which has properties similar to the enzyme in chloroplasts of higher plants.

Glycerol concentrations in crop plants

Abstract A procedure has been developed for preparation of plant extracts for quantitation of their glycerol content using high performance liquid chromatography or enzymatic analysis. Fifteen crop plants grown under field conditions had leaf concentrations of glycerol between 10 and 39 μg/g wt weight of tissue. Approximately 12 h after relatively heavy rains leaves of maize, sugar beet, soybean, bean, pumpkin and alfalfa had several fold increases in concentrations of leaf glycerol. When barley plants were made anaerobic for 24 h, large increases in leaf glycerol concentrations were observed. It is proposed that part of the glycerol observed in anaerobic plants comes from glycerol synthesis in the root and transport to the leaves and part is produced in the leaves.

Ornithine as a precursor for the pyrrolidine ring of nicotine

Abstract Radioactive nicotine, from Nicotiana rustica plants which had been fed [2-14C]-ornithine, was degraded with recovery of C-5 of the pyrrolidine ring. This position of the ring was shown to have about half of the radioactivity of the original nicotine. The remaining radioactivity was in the residual carbon skeleton of the nicotine which was isolated as a derivative of a substituted primary amine. A previous degradation had established that the radioactivity in the amine derivative was in the carbon atom corresponding to position 2 of the pyrrolidine ring of nicotine. This pattern of labelling supports the postulation of one or more symmetrical intermediates in the synthesis of the pyrrolidine ring of nicotine from the amino acid ornithine.

Biogenesis of Nicotine

Radioactive nicotine was synthesized by Nicotiana rustica L. which was fed sodium acetate-1-C14, sodium acetate-2-C14, sodium pyruvate-1-C14, or sodium pyruvate-3-C14. Acetate-2-C14 and pyruvate-3-C14 were converted to nicotine with the least dilution of radioisotope, whereas pyruvate-1-C14 was incorporated with a relatively large dilution. When acetate-1-C14 was administered to the plants the nicotine contained C14 only in the pyrrolidine ring. After acetate-2-C14 was fed, C14 was located in both the pyrrolidine and pyridine rings.

The role of the pyridine nucleotide cycle in the biosynthesis of ricinine

Abstract Competitive feeding experiments were performed using castor bean seedlings to determine the effect of NAD on the incorporation of radioactive quinolinic acid into the alkaloid ricinine. The exogenous NAD did not cause a decrease in the total radioactivity incorporated into the ricinine as expected, but instead caused an increase. Data previously presented by other investigators was re-examined in light of this new finding. It was concluded that the existing evidence supports the hypothesis that NAD and ricinine are made from quinolinic acid by separate pathways.

The incorporation of Δ1-pyrroline-5-carboxylic acid into nicotine

Abstract dl -Δ1-Pyrroline-5-carboxylic acid-5-14C, a possible precursor of nicotine, was fed to Nicotiana rustica for 6 hr. The following percentage distribution of 14C was found after partial degradation of the isolated nicotine:pyridine ring, 5·9 per cent; carbon 2′, 47·8 per cent; and carbon 3′, 1·1 per cent. More than 40% of the remaining radioactivity was located in carbon 5′. Although dl -Δ1-pyrroline-5-carboxylic acid-5-14C was incorporated symmetrically as are other precursors of the pyrrolidine ring of nicotine, its low incorporation into nicotine (0·04 per cent) indicates that it probably is not on the main pathway of pyrrolidine ring biosynthesis.

Nicotine Oxidation by Arthrobacter

Summary A gram negative, non-motile bacterium isolated from tobacco plant roots was identified as a member of the genus Arthrobacter. The organism had the ability to convert nicotine to 6-hydroxynicotine. Maximum concentration of 6-hydroxynicotine detectable in the culture medium was approximately 50% of initial nicotine concentration on a molar basis. The identity of the product was established by its melting point, and the melting point of its picrate, its specific rotation, elementary analysis, and ultraviolet and infrared absorption spectra.

Influence of alpha-naphthylthiourea (ANTU) on iodine metabolism.

Summary Total, inorganic, and organic iodine of the tissues of normal and ANTU-poisoned rats was measured. ANTU decreased the thyroid iodine of rats and guinea pigs and caused a small increase in the total iodine of blood and lung when acutely toxic doses of the rodenticide were administered. Feeding a high iodine diet for 5 days caused a marked increase in the total iodine of tissues from normal and thyroidectomized rats. Since pre-treatment of thyroidectomized rats with iodine does not afford protection against ANTU the increase in thyroid iodine of normal iodine-fed rats appears to be involved directly in the prophylactic effect of iodide against ANTU poisoning.