Effects of the lysine analog S-2-aminoethyl-L-cysteine on growth and metabolism of germinating barley, H̲o̲ṟḏe̲u̲m̲ v̲u̲ḻg̲a̲ṟe̲ L.

The effects of the lysine structural analog, S-2-aminoethyl-Lcysteine (AEC), on germination and seedling growth of barley, Hordeum vulgare L., were studied. The AEC was inhibitory to germination and subsequent seedling growth. Lysine relieved growth inhibition caused by AEC. The appearance of α-amylase (E.C. 3.2.l.l.) activity in liquid incubation media of embryo-less barley half-seeds was inhibited by AEC. The reduced level of medium α-amylase activity did not appear to be attributable to an impaired aleurone secretory process because a parallel accumulation of enzyme activity was not found in this tissue. It may be, however, that AEc is inhibitory to secretion, to some extent, because a lower level of protein was detected in the media of half-seeds incubated in the presence of AEC. The level of reducing sugars released from endosperm starch, an indirect measure of α-amylase activity, was also decreased if half-seeds were exposed to AEC. When equimolar amounts of AEC and lysine were supplied to half-seed incubation media, the levels of α-amylase, reducing sugars and protein were restored to control values. The AEC appeared to be competing with lysine for incorporation into newly synthesized aleurone protein. These results are consistent with the hypothesis that AEc is functioning as a lysine antagonist in germinating barley seeds.