Expression of an engineered acidic-subunit 11S globulin of amaranth carrying the antihypertensive peptides VY, in transgenic tomato fruits

The acidic-subunit of amarantin, main seed storage protein of Amaranthus hypochondriacus, carrying four antihypertensive biopeptides Val-Tyr was expressed in the fruit of transgenic tomato plants. Immunoblot analyses indicate that the expressed recombinant protein was stably accumulated at levels up to 12.71 % with respect to total protein content of transgenic fruits. There was a remarkable change in total protein content (5-22 % increase) of transgenic tomato fruits compared to non-transformed samples. Specific increases of the essential amino acids valine (31-40 %), tyrosine (29-34 %), isoleucine (21-31 %), leucine (28-31 %) and phenylalanine (28-29 %) were also detected in some transgenic lines versus wild type lines. Protein hydrolysates from transgenic tomato fruits showed in vitro inhibition of the angiotensin converting enzyme, with IC₅₀ values that ranged from 0.376 to 3.241 μg ml^-1; this represents an increase of up to 13-fold in the inhibitory activity compared with the protein hydrolysates of non-transformed fruits. These results suggest the possible application of transgenic tomato fruit for massive production of this engineered version of amarantin, which could be especially useful in the prevention and control of hypertension.