Hydrolysis of Gliadin during Germination of Wheat Seeds

The in vivodegradation of gliadin has been studied using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reversed-phase high performance liquid chromatography. Both analyses show the appearance of a small number of degradation products and the early disappearance of some gliadin components during the course of germination. These components thus appear to be subject to preferential breakdown, the w-gliadin fraction being the first to be degraded. The in vitrodegradation of total gliadin or selected gliadin fractions, performed by the main endopeptidase appearing during wheat germination, reveals a transient accumulation of intermediates, which were subsequently degraded to small peptides. These data suggest that the relatively small amount of intermediates formed during wheat germination might be due to the concerted action of the cysteine proteinase and of the carboxypeptidases. Since these enzymes have high activities during the course of seed germination, they might cause a rapid degradation of intermediates before they can accumulate.