Characterisation, immunolocalisation and antifungal activity of a lipid transfer protein from chili pepper (Capsicum annuum) seeds with novel α-amylase inhibitory properties

Lipid transfer proteins (LTPs) were thus named because they facilitate the transfer of lipids between membranes in vitro. This study was triggered by the characterization of a 9-kDa LTP from Capsicum annuum seeds that we call Ca-LTP1. Ca-LTP1 was repurified, and in the last chromatographic purification step, propanol was used as the solvent in place of acetonitrile to maintain the protein's biological activity. Bidimensional electrophoresis of the 9-kDa band, which corresponds to the purified Ca-LTP1, showed the presence of three isoforms with isoelectric points (pIs) of 6.0, 8.5 and 9.5. Circular dichroism (CD) analysis suggested a predominance of alpha-helices, as expected for the structure of an LTP family member. LTPs immunorelated to Ca-LTP1 from C. annuum were also detected by western blotting in exudates released from C. annuum seeds and also in other Capsicum species. The tissue and subcellular localization of Ca-LTP1 indicated that it was mainly localized within dense vesicles. In addition, isolated Ca-LTP1 exhibited antifungal activity against Colletotrichum lindemunthianum, and especially against Candida tropicalis, causing several morphological changes to the cells including the formation of pseudohyphae. Ca-LTP1 also caused the yeast plasma membrane to be permeable to the dye SYTOX green, as verified by fluorescence microscopy. We also found that Ca-LTP1 is able to inhibit mammalian alpha-amylase activity in vitro.