Terence A. Smith

Polyamines in barley seedlings

Abstract Polyamine levels in barley seedlings grown in the dark or in diurnal illumination have been determined, by direct dansylation, 3, 6 and 12 days after g

Phenethylamine and related compounds in plants

Abstract A comprehensive and up-to-date listing is provided of the distribution of phenethylamines in the Plant Kingdom. Such a listing is of importance because of their considerable physiological activity in higher animals. Their distribution in plants is also of some taxonomic interest.

Recent advances in the biochemistry of plant amines

Abstract Simple aliphatic monoamines are formed in the red algae by a non-specific amino acid carboxy-lyase. An aldehyde-amino acid transaminase with broad substrate specificity is the mechanism for the formation of these amines in many higher plants. Putrescine accumulates in response to potassium and magnesium deficiency, and the amount of this diamine is greatly increased on supplying nitrogen as ammonium salts. Putrescine is also found at high levels in rapidly growing tissues. Cadaverine occurs in several leguminous plants. Putrescine, spermidine and spermine have been detected in many different species of plants, and they are probably ubiquitous. The polyamines are probably synthesized in plants by the pathways already demonstrated in animals and micro-organisms. Several new polyamine alkaloids have been characterized. Amine oxidases are probably involved in the formation of nicotine and indol-3yl-acetic acid. The amine oxidases from the Leguminosae and Gramineae have been further characterized. Carboxy-lyases have been demonstrated for tryptophan, tyrosine and DOPA. Cacti contain a large variety of phenethylamine derivatives related to mescaline.

Amine levels in mineral-deficient Hordeum vulgare leaves

Abstract In potassium-deficient barley leaves, on the basis of fresh weight, putrescine was 13·3-fold greater and in magnesium deficiency 3-8-fold greater than controls. Putrescine was found to be reduced in phosphorus (× 0·6), sulphur (× 0·5) and nitrogen (× 0·2) deficiencies and on substituting nitrate for ammonium (× 0·2). Calcium deficiency and high salt (KCl) increased putrescine by 1·5-fold. High KCl reduced spermidine levels (× 0·2) without a corresponding reduction in spermine levels. The agmatine content was enhanced in magnesium- (× 2·5) and potassium- (× 5) deficient plants, while the arginine was increased × 1·4 and × 2·0 respectively on a fresh weight basis. Compounds tentatively identified as diaminopropane and 1-(3-aminopropyl)pyrroline were increased significantly with high KCl and low calcium. No homospermidine or diaminodipropylamine could be detected in any of the extracts, but traces of cadaverine may be present.

Putrescine, spermidine and spermine in higher plants.

Abstract The diamine, putrescine and the polyamines spermidine and spermine have been estimated quantitatively in the leaves of a number of higher plants. In six species grown in potassium-deficient conditions, by comparison with normal plants, the mean increase in the concentration of putrescine was 16·6-fold, for spermidine 1·9-fold and for spermine 1·2-fold. This is compatible with a metabolic pathway in which spermidine and spermine are derived consecutively from putrescine.

Effect of mineral deficiency on amine formation in higher plants

Abstract Potassium deficiency caused putrescine accumulation in the leaves of barley, radish, pea, bean and spinach plants. Magnesium deficiency caused putrescine accumulation in barley, pea and bean leaves, and also in the leaves of older radish plants. In young radish plants less putrescine was found in magnesium deficiency, and in spinach magnesium deficiency was without effect on putrescine levels. Putrescine content may be a useful guide to the mineral status of legumes, since accumulation of this amine may be detected before deficiency symptoms appear. Radioactivity from l -arginine-[U- 14 C] fed to barley seedlings was detected in agmatine within 2 hr, and probably also in the hordatines after 24 hr, feeding. After 2 hr the label in the agmatine was greatest in the potassium-deficient plants, but after 24 hr the level declined to that found in the agmatine of the leaves of the magnesium-deficient and control seedlings. The rate of putrescine formation was high in both potassium and magnesium deficiency. Incorporation of radioactivity in spermidine and spermine on feeding putrescine-[1,4- 14 C] to barley seedlings was estimated in the dansylated amines after separation by TLC. Activity was higher in spermidine and lower in spermine in the potassium-deficient plants than in the controls. The spermidine/spermine ratio declined on excision of barley leaves.

Distribution of the hordatines in barley

Abstract Concentrations of agmatine, coumarylagmatine and the antifungal hordatines in the shoots of barley seedlings have been determined at various stages of growth. Coumarylagmatine declined with age on a fresh weight basis, both in diurnal illumination and in continuous darkness. Hordatines A and B (estimated together) declined in the light to the 30th day after germination but their concentrations were stable in the dark to the 12th day. Hordatine M declined in the light to the 30th day and in the dark to the 12th day from germination. Agmatine declined in both light and dark to the 12th day. On the 30th day from germination potassium deficiency caused an increase in hordatines A + B ( × 6), hordatine M ( × 2) and agmatine ( × 13). Infection of the 11-day-old seedlings with mildew ( Erysiphe graminis ) caused an increase in the content of hordatine A + B ( × 6), hordatine M ( × 2) and agmatine ( × 2) 13 days later. Hordatines occurred in seedlings of H. bulbosum , H. distichon , H. murinum and H. spontaneum , though not in seedlings of H. jubatum , maize, millet, oats, rice, rye or wheat. Arginine decarboxylase activity declined with age in barley seedlings grown in the light or dark from the 3rd to the 12th day.

Arginine decarboxylase of oat seedlings

Abstract Arginine decarboxylase activity in the shoots of seedlings was high in oats, intermediate in barley and low in rice, maize, wheat and rye. After partial purification, the arginine decarboxylase from the shoots of potassium deficient oat seedlings was separated into two fractions, A (MW 195 000) and B (MW 118 000), by gel chromatography. On gel electrophoresis, the mobilities of these fractions were respectively 0.12 and 0.55 relative to bromophenol blue at pH 9.5. Fraction A was twice as active as fraction B in extracts of seedlings grown with both normal and potassium deficient nutrition, despite the greater activity ( × 5) of the potassium deficient plants. The properties of the two fractions were similar with respect to pH optimum (7–7.5), K m (3 × 10 −5 M) and the effect of inhibitors. Fraction A was purified to apparent homogeneity by DEAE-cellulose chromatography. The enzyme was specific for l -arginine and it was strongly inhibited by NSD 1055, d -arginine and canavanine. Mercaptoethanol and dithiothreitol stimulated the enzyme by ca 50% and p -chloromercuribenzoate was an inhibitor. Pyridoxal phosphate stimulated activity by ca 30% and EDTA stimulated activity by 30%. Ca 2+ and Mg 2+ inhibited the enzyme by 50% at ca 20 mM. Putrescine and the polyamines showed only moderate inhibition at 10 mM, but agmatine reduced activity to 30% at this concentration.

Purification and properties of the polyamine oxidase of barley plants

Abstract The polyamine oxidase of barley shoots is associated with a particle which sediments in low centrifugal fields. The enzyme was removed from these particles by washing in 0·5 M NaCl and then purified about 24-fold. The purified enzyme oxidized spermine stoicheiometrically to 1,3-diaminopropane and 1-(3-aminopropyl)pyrroline (pH optimum 4·0). Spermidine was oxidized to 1,3-diaminopropane and 1-pyrroline (pH optimum 6·6). At their respective pH optima, spermine is oxidized about 30 times faster than spermidine. Hydrogen peroxide was formed in the course of the polyamine oxidation. The enzyme was not sensitive to several copper chelating reagents but 2-hydroxyethylhydrazine caused 50% inhibition at 5 × 10 −4 M. The enzyme was also present in particles in the roots of barley seedlings and in extracts of the leaves of oats, maize, rye and wheat.

Tryptamine and related compounds in plants

Abstract The occurrence of the tryptamines and related compounds in fungi and higher plants is listed on a taxonomic basis. Several of these amines have considerable physiological activity in higher animals.