A protein with amino acid sequence homology to bovine insulin is present in the legume Vigna unguiculata (cowpea)

Abstract

Since the discovery of bovine insulin in plants, much effort has been devoted to the characterization of these proteins and elucidation of their functions. We report here the isolation of a protein with similar molecular mass and same amino acid sequence to bovine insulin from developing fruits of cowpea (Vigna unguiculata) genotype Epace 10. Insulin was measured by ELISA using an anti-human insulin antibody and was detected both in empty pods and seed coats but not in the embryo. The highest concentrations (about 0.5 ng/µg of protein) of the protein were detected in seed coats at 16 and 18 days after pollination, and the values were 1.6 to 4.0 times higher than those found for isolated pods tested on any day. N-terminal amino acid sequencing of insulin was performed on the protein purified by C 4 -HPLC. The significance of the presence of insulin in these plant tissues is not fully understood but we speculate that it may be involved in the transport of carbohydrate to the fruit.

Isolation and intracellular localization of insulin-like proteins from leaves of Bauhinia variegata

“…While it has been previously shown that insulin is present in the testa of C. ensiformis (11), in developing fruits of Vigna unguiculata (12) and in M. charantia seeds (13), its functions in plants are not clear at present (23). Nevertheless, its localization in these tissues and the timing of its appearance suggest that insulin in plants has metabolic functions similar to those it exerts on animals, at least in connection with carbohydrate metabolism (23).…”

“…Bioactive and immunoactive insulins were detected in the unicellular eukaryotes Neurospora crassa and Aspergillus fumigatus, which are fungi, in Tetrahymena pyriformis, a ciliated protozoon (9), and in the prokaryote Escherichia coli (10). Also, Oliveira et al (11) and Venâncio et al (12) isolated proteins from the testa of Canavalia ensiformis seeds and from fruits of Vigna unguiculata, respectively, and showed that they have amino acid sequences identical to that of bovine insulin. A hypoglycemic polypeptide was extracted from M. charantia seeds.…”

Immunodetection and quantification of insulin-like antigens in sprouts: development of an efficient functional food

“…This 4 kDa peptide stimulates protein kinase activity of Bg and regulates the growth and cell proliferation of plant callus [6]. A protein with amino acid sequence homology to bovine insulin was shown to be present in the developing fruits of cowpeas [7]. This evidence suggests the possible role of insulin-like proteins in growth, cell proliferation, and sugar transport, during seed germination.…”

From Pancreatic to Non-Pancreatic Insulin: A Miraculous Journey

“…Insulin-like proteins was isolated from the leaves or aerial parts of Bryophyta (mosses), whisk ferns (Psilotum nudum), Lycopodophyta (Selaginella), Sphenopsida (horsetails, Equisetum, many gymnosperms (Coniferophyta, Cycadophyta, Ginkgophyta), angiosperms (flowering plants including monocotyledons and dicotyledons) Gracilariopsis (red alga), Spirulina maxima (Cyanobacterium) and yeast (Saccharomyces cerevisiae) using modified ELISA and Western Blotting (Silva et al, 2002). Venancio et al (2003) isolated insulin like proteins from seeds coat of Vigna unguiculata at 16 and18 days after pollination whose RP-HPLC analysis and amino acid sequence was identical to that of bovine insulin (Table 2). Its highest concentration was found in the empty pods and seed coats and not in the embryo, suggesting its involvement in carbohydrate metabolism in facilitating glucose transport across membranes, similar to its role in animals.…”