A matured maize kernel contains about 8%-10% of proteins,and about 80% of them are endosperm storage proteins mainly consisted of prolamins（zeins）.Maize zeins are divided into 4 subclasses of α,β,γ and δ types.Among these,α-type has two components of 19 kDa and 22 kDa α-ziens,β-type has only one component of 15 kDa β-zein,and γ-type has three components of 16 kDa,27 kDa and 50 kDa γ-zeins,whereas δ-type has two components of 10 kDa and 18 kDa δ-zeins.α-zeins with 1%-2% of methionine comprise over 70% of the total zeins,whereas β-zeins accounts for 20% with about 10% of methionine.Methionine-rich γ-and δ-zeins accumulates at low levels in the matured kernels,in which the highest content of methionine are 21% and 37%,respectively.Zeins are encoded by 65-100 genes of multigene families located on various chromosomes;of these,structural gene of 10 kDa δ-zeins,dzs10,have been utilized in high-methionine transgenic breeding.%成熟的玉米籽粒中蛋白质含量为8%～10%,其中,约80%为胚乳蛋白,主要由被称为醇溶蛋白（zein）的胚乳贮存蛋白所构成。玉米醇溶蛋白分为α,β,γ和δ等4种类型,其中,α类型包含19kDa和22kDaα-醇溶蛋白2个组分,β类型只有15kDaβ-醇溶蛋白1种,γ类型包含16kDa、27kDa和50kDaγ-醇溶蛋白等3个组分,而δ类型包含10kDa和18kDaδ-醇溶蛋白等2个组分。在玉米醇溶蛋白中,α类型占70%以上,但其蛋氨酸含量非常低,只有1%～2%。约占20%的β类型,其蛋氨酸含量约10%。γ类型和δ类型的醇溶蛋白在胚乳中的含量很少,但这两类醇溶蛋白的蛋氨酸含量很高,最高分别达到21%和37%。不同的醇溶蛋白由分属于不同多基因家族的基因所编码,涉及到65～100个基因,这些基因存在于不同的染色体上;其中10kDaδ-醇溶蛋白的结构基因dzs10已在高蛋氨酸转基因育种中得到应用。
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