The mobilization of storage proteins in germinating Vicia faba

Bonner, PLR ORCID: https://orcid.org/0000-0001-9015-3403, 1984. The mobilization of storage proteins in germinating Vicia faba. PhD, Nottingham Trent University.

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Abstract

Proteolysis in germinating Vicia faba has been investigated in two ways. Firstly, by isolating and characterising two protease enzymes and secondly, by examining the reserve proteins present in seeds at different times during germination.

One of the enzymes was a proteinase with an apparent molecular weight of 12,000 daltons, the other an aminopeptidase with a molecular weight of 50,000 daltons, both molecular weights estimated by gel filtration. The enzymes were inhibited by N-ethylmaleimide, iodoacetamide and p-chloromercuri- benzene sulphonic acid, whilst their activity was stimulated by reducing agents, indicating the presence of a thiol group at their active sites. The proteinase had a pH optima of 5.4 and was active on the storage proteins legumin and vicilin isolated from days O, 4, 7 and 11 germinated seeds, as well as the nitrophenol esters of asparagine and glycine. The peptidase had a pH optima of 7.4 and showed no activity on the storage proteins legumin and vicilin, but was active on a variety of di- and tri-peptides, prefering glycine as the N-terminal residue next to a hydrophobic amino acid containing an aromatic residue. Antibodies raised to the peptidase in rabbits were used to show that there is an antigenically similar enzyme in cotyledons of Pisum sativum, Vigna radiata, Phaseolusvulgaris and another variety of Vicia faba. Green Windsor, but not in cereal seeds.

Legumin and vicilin were isolated from seeds at various stages of germination and checked for purity by Zonal isoelectric precipitation electrophoresis, a method developed during this study. Using PAGE, SDS-PAGE and lEF in dissociating and reducing conditions, the storage proteins were shown to alter in composition as germination proceeded. Larger subunits disappeared whilst smaller subunits accumulated. These changes were more apparent in vicilin than legumin.

Item Type:	Thesis
Creators:	Bonner, P.L.R.
Date:	1984
ISBN:	9781369325836
Identifiers:	Number Type PQ10290334 Other
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Ward
Date Added:	08 Jul 2021 10:20
Last Modified:	22 May 2024 15:18
URI:	https://irep.ntu.ac.uk/id/eprint/43383

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