Department of Fermentation Science, Faculty of Applied Bio-Science, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
Gene. 2012 Jan 15;492(1):244-9. doi: 10.1016/j.gene.2011.10.021. Epub 2011 Oct 25.
Lysozyme (LZ), a bacteriolytic enzyme, is found in the egg white of many avian eggs and plays an important role in host defense; however, LZ activity in emu (Dromaius novaehollandiae) egg white is exceptionally undetectable. We cloned and characterized emu goose-type LZ (LZG) and chicken-type LZ (LZC) genes. RT-PCR analysis revealed very low LZG gene expression levels and absence of LZC gene expression in the emu oviduct. Sequencing of full-length LZG and LZC cDNAs indicated that their amino acid sequences show high similarities to ostrich LZG and LZC, respectively, with conserved catalytic residues for enzymatic activities. Whereas recombinant emu LZG prepared using Pichia pastoris exhibited similar enzyme activity as ostrich LZG, recombinant emu LZC exhibited significantly higher lytic activity than chicken LZC. We concluded that emus have functional genes for both LZG and LZC like many other avians, and the LZG gene is expressed in oviduct probably as in other ratite, however, its expression levels in egg white were low to be detected.
溶菌酶（LZ）是一种存在于许多禽类蛋清中的溶菌酶，在宿主防御中发挥重要作用；然而，鸸鹋（Dromaius novaehollandiae）蛋清中的 LZ 活性却异常难以检测到。我们克隆并鉴定了鸸鹋鹅型 LZ（LZG）和鸡型 LZ（LZC）基因。RT-PCR 分析显示，鸸鹋输卵管中 LZG 基因表达水平极低，且不存在 LZC 基因表达。全长 LZG 和 LZC cDNA 的测序表明，它们的氨基酸序列分别与鸵鸟的 LZG 和 LZC 高度相似，具有酶活性的保守催化残基。虽然使用巴斯德毕赤酵母制备的重组鸸鹋 LZG 表现出与鸵鸟 LZG 相似的酶活性，但重组鸸鹋 LZC 的裂解活性明显高于鸡 LZC。我们得出结论，鸸鹋像许多其他禽类一样，具有功能性的 LZG 和 LZC 基因，LZG 基因在输卵管中表达，可能与其他平胸鸟类一样，但其在蛋清中的表达水平低到难以检测。
