The determination of glutamine in the presence of asparagine

Abstract

ALTHOUGH glutamine has been known for many years to be a constituent of certain plant tissues [Schulze and Bosshard, 1883], no method whereby this substance can be separately distinguished from asparagine and determined with accuracy has appeared until recently. Glutamine has indeed frequently been isolated but its properties are such that isolation has only qualitative significance. Chibnall and Westall [1932] noted that the amide group ofglutamine is extensively hydrolysed by heating at 1000 for 3 hours at PH 8, whereas asparagine is scarcely affected by this treatment. Accordingly they suggested that the glutamine

The Physiology of Growth in Apple Fruits V. Soluble Nitrogen Constituents

“…(f) Estimation of Amide Nitrogen Amide nitrogen was estimated by the method of Vickery et al (1935) on aqueous extracts of dried tissue.…”

Determination of Free Ammonium and Asparagine and Glutamine Amide-Nitrogen in Extracts of Plant Tissue

“…Vickery et al (8) compared the levels of free ammonium and the amides in extracts from different plant tissues which had been extracted in the fresh state or after being dried at elevated temperatures. In general, the extracts from dried leaf tissue contained more free ammonium and less asparagine and less glutamine than the extracts from fresh leaf tissue.…”

“…However, the direction and/or magnitude of change in the level of free ammonium and the amides, due to drying the plant material, varied between different tissues, making comparative sttudies of the levels of these compotunds in different tissues of the same plant difficult to interpret. In order to have a uniform source of plant material for extraction and analysis and to prevent the variable changes in the levels of free ammonium and the amides during drying as described by Vickery et al (8), the barley shoots used in the present sttudy were freeze-dried by lyophilization, finely ground in a Wiley Mill, and stored at -15°in the absence of moisture until extraction.…”

“…The high levels of the amides and the low level of free ammoniuim present in the tissue extracts indicated that the extraction and analytical procedures resutlted in little if any hydrolysis of the amides. Methods (3,8,9) often employed to estimate the levels of free ammonium, asparagine, and glutamine in extracts of plant tissule have the disadvantage of requiiring a time-consuiming distillation step in the determination of free ammonium. This distillation step, unless controlledl very careftlly, can restult in the partial hydrolysis of the amide bond of glutamitne and the stubseqtuent recovery of this amidenitrogen with the free-ammonitum fraction.…”

“…Althouigh these methods have the advanitage of being more specific than the differential acid-hydrolysis procedure (8,9) uisually' employecl for the estimation of asparagine and glutamine in the same soltutioin, the presence of free ammoniuim in the extracts of plants uinder certain (8,9). Ammonium-nitrogen released duiring each hydrolysis step was estimate(l by the direct nesslerization procedulre.…”