Randhir Singh

Isolation and characterization of fructosyltransferase from chicory roots

Abstract The occurrence of fructosyltransferase was demonstrated in the roots of chicory. The enzyme was purified 14-fold by ammonium sulphate fractionation and sephadex column chromatography. The optimal conditions for activity were pH 5·6, 37° and substrate (sucrose) concentration of 5·84 × 10 −1 M. The K m of the enzyme was found to be 2·85 × 10 −1 M. The enzyme was completely inactivated at 62·5°. Neither dialysis nor addition of inorganic phosphate affected its activity. The enzyme was capable of synthesizing glucofructosans from sucrose alone with the simultaneous release of glucose until seven oligosaccharides were synthesized, and with progressive enzyme activity small quantities of fructose were also released. Ag + and Hg 2+ completely inhibited the enzyme action, whereas, Cu 2+ , Zn 2+ , Fe 2+ , Na + , K + and Ca 2+ had almost no effect. The enzyme activity was significantly increased by Mn 2+ , Mg 2+ , Co 2+ and Ni 2+ .

Effect of water stress on some enzymes of nitrogen metabolism in pigeonpea

Abstract Water stress created by withholding irrigation at flowering stage (70 days) in pigeonpea resulted in decreased water potential of roots, nodules and leaves. The decreased water potential in nodules resulted in decreased activities of nitrogenase, glutamine synthetase, glutamate dehydrogenase and uricase. However, the activity of allantoinase increased under mild stress with a slight decrease under severe stress. This corresponded with a simultaneous increase in allantoic acid content. Uricase and allantoinase could not be detected in roots and leaves of both control and stressed plants. In roots, the activities of GS and GDH decreased under stress, whereas in leaves, their activities were not affected. Although the water potential recovered in different organs of the stressed plant on re-irrigation, the recovery in the case of some enzymes was not complete.

Substrate specificity of fructosyl transferase from chicory roots

Abstract The substrate specificity of the enzyme, fructosyl transferase (sucrose-sucrose 1-fructosyl transferase) from chicory root was studied by incubating a number of sugars, alone and in combination, with the enzyme. Sucrose was found to be the true substrate. The oligosaccharide synthesized from sucrose was identified as the trisaccharide 1 F -fructosyl sucrose.

Enzymes of glutamine metabolism in testa-pericarp and endosperm of developing wheat grain

Abstract Glutamate dehydrogenase, glutamine synthetase, glutamate synthase, glutamate puruvate transaminase and glutamate oxaloacetate transaminase have been assayed in developing testa-pericarp and endosperm of two wheat varieties, namely Shera (11.6% protein) and C-306 (9.8% protein). On per organ basis, activities of all the enzymes studied, except glutamine synthetase, increased during development. Glutamine synthetase activity decreased during development in the testa-pericarp, whereas, no glutamine synthetase activity could be detected in endosperm of either variety at any stage of development. Compared to testa-pericarp, endosperm had higher activities of glutamate synthase and glutamate pyruvate transaminase. On the whole, enzyme activities in Shera were higher, as compared to C-306. Developmental patterns and relative levels of enzyme activities in the two varieties were more or less the same, when expressed on dry weight basis or as specific activities. The results suggest that ammonia assimilation in developing wheat grain takes place by the glutamate dehydrogenase pathway in the endosperm; and both by the glutamate dehydrogenase and glutamine synthetase—glutamate synthase pathways in the testa-pericarp.

Alkaline inorganic pyrophosphatase from guar (Cyamopsis tetragonoloba) cotyledons

Abstract Alkaline inorganic pyrophosphatase from guar cotyledons was purified x 110 with about 34% recovery by (NH 4 ) 2 SO 4 fractionation, acetone prec

Nitrogenous compounds and protease activity in developing testapericarp and endosperm of high and low protein wheat (Triticum aestivum L.)

Nitrogenous compounds such as total protein, true protein, soluble protein, non-protein nitrogen, total amides, ammonium, nitrate, nitrite, free amino acids and neutral and acid protease activities were estimated in a high protein wheat cv Shera (12·8% protein) and a relatively low protein wheat cv C-306 (10·4% protein) at different stages of grain development. All the nitrogenous compounds studied, as well as protease activities, were located in both testa-pericarp and endosperm. Developmental patterns and relative levels were, more or less, similar when expressed on per organ basis, or on dry weight basis. In the testa-pericarp; dry weight, total protein, soluble protein, true protein, amide, ammonium, nitrate and nitrite contents increased during development, and were higher in Shera, compared with cv C-306. Non-protein nitrogen content decreased during pericarp development, and was higher in cv Shera, compared with cv C-306. Free amino acid content and protease activities decreased in developing pericarp, and were lower in cv Shera, compared with cv C-306. Similar developmental patterns and relative levels of nitrogenous compounds and protease activities were found in endosperm. It is suggested that both testa—pericarp and endosperm make qualitatively similar contributions to the accumulation of nitrogenous compounds in developing wheat grain; higher protease activity in the endosperm of C-306 is not responsible for lower protein accumulation, and nitrate and nitrite are assimilated mainly in the green pericarp of the wheat grain. It appears that differences in protein contents of Shera and C-306 wheat arise primarily from differences in translocation of nitrogenous solutes from the phloem sap to the peduncle and pericarp, enroute endosperm.

Assimilate supply in relation to grain weight in wheat (Triticum aestivum L)

The contents of various free sugars in large and small wheat grains were compared with those in normal grains at different stages of grain development. Their content paralleled grain weight only upto 14 days after anthesis (A+14). On a dry weight basis, no positive correlations were observed between the concentrations of various free sugars and grain weight at any of the stages. Differences in grain weight were dependent mainly on the number of cells formed in the endosperm which in turn seemed to be regulated by the assimilate supply available to the grain during the first 14daa.