VARIABILITY AND MODIFICATION OF THE LECTINS OF SOME MEMBERS OF THE PAPILIONOIDEAE

The aims of this study were to investigate the variability of lectins of leguminous plants, assessing differences between species, between cultivars of the same species and within the plant itself, and also the potential modification of such lectin activity. Three sources of material were investigated for haemagglutinating activity. (1). Lathyrus L. seeds. All haemagglutinin-positive samples caused relatively weak, non-specific agglutination of human erythrocytes and detected the 'Hi-agglutinogen’ present on the erythrocyte surfaces of laying-chickens (21 previously unreported species). (2). Lupinus L. seeds. Very weak or no agglutination of human or rabbit erythrocytes was detected using complete or incomplete haemagglutination techniques. (3). Vegetable organs of common legumes. Of the range of samples tested, significant levels of haemagglutinating activity were detected only in the roots and stem of the scarlet runner bean (Phaseolus coccineus L. previously unreported). In order to clarify apparent discrepancies in the literature, the lectins from sweet peas (Lathyrus odoratus L. cv Galaxy Rose Pink) were purified using affinity chromatography by SDS-PAGE yielded values of 17,800 and 6,200, giving an overall stoichiometry of ex,, . Three isolectins were separated by isoelectric-focussing. Isolation and partial purification of lectins from P. coccineus L. roots yielded two haemagglutinin-positive fractions (f3 & f5), the latter possessing potent anti-chicken activity. Similarly a single fraction was obtained from stem extracts. Marked enhancements of haemagglutination titre was achieved by using protease treated erythrocytes, particulary amongst Lupinus L. species (maximally 1:8192 and 1:9096 for L. albus and L. mutabilis Sweet respectively). Chemical modification studies on L. odoratus L. seed and P. coccineus L. root lectins demonstrated the importance of the ^-amino groups of lysine in the carbohydrate binding sites of such lectins. No alteration of blood-group specificity was acheived by either enzymic or chemical modification reactions. AIMS The aims of this thesis are to investigate the variability and modification of plant lectins, as found in the Leguminosae. Following a survey of the literature, three areas were chosen for investigation. (1) Lathyrus L. species ; seeds These were chosen because of their ability to distinguish the "Hi agglutinogen present on the surface of laying-chicken erythrocytes. Also Lathyrus odoratus had been previously isolated, but considerable discrepancies in molecular weight and subunit conformation existed . The isolectins from cv. "Galaxy Rose Pink" were isolated and characterised to help clarify this situation. (2) Lupinus L. species : seeds Previous reports in the literature indicated that most samples tested were devoid of haemagglutinating activity against human and animal. Further attempts were made to survey the occurrence of agglutinins in these species using both untreated and enzyme pretreated erythrocytes. (3) Vegetative organs of common legumes. The occurrence of lectins outside of seed has been poorly documented with many conflicting reports. It was decided to survey the vegetative organs of a number of common legumes for haemagglutinating activity, and if possible compare any vegetative agglutinins with those found in the corresponding seeds. To this end, isolation and partial characterisation of P. coccineus root and stem lectins was undertaken. Attempts to modify lectin activity, both in terms of alteration of blood group specificity and in enhancement of haemagglutination titre, were made by employing modification of the erythrocyte surface using proteolytic enzymes and by direct chemical modification of the lectins themselves.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

1984

Author dc:creator

• SPENCER, I. W.

Licence

• https://dora.dmu.ac.uk/bitstreams/0b1d6979-f664-4dca-bf57-8b0d9875f329/download