McKenzie H A
School of Chemistry, University College, University of New South Wales, Australian Defence Force Academy, Canberra, Australia.
EXS. 1996;75:365-409.
Lysozyme is ubiquitous in a variety of tissues and secretions. Chick-type (c-type) lysozymes lyse the cell walls of certain bacteria. In contrast, alpha-lactalbumin appears to occur only in mammalian milk and colostrum. It has the unusual property of acting as a modifier protein to modify the action of galactosyl transferase to a lactose synthase. Both proteins have diverged from a common ancestor. This is reflected in the striking relationship between their amino acid sequences, and the high conservation of disulfide bridges, their intron-exon organization, and three-dimensional structures. In studying their evolutionary relationships some important differences are noted, e.g., all alpha-lactalbumins strongly bind Ca(II), but only some c-type lysozymes do so. These properties point the way to future investigations that are necessary before firm conclusions can be made about their evolutionary history.
溶菌酶在多种组织和分泌物中普遍存在。鸡型（c型）溶菌酶可溶解某些细菌的细胞壁。相比之下，α-乳白蛋白似乎仅存在于哺乳动物的乳汁和初乳中。它具有作为修饰蛋白来改变半乳糖基转移酶对乳糖合酶作用的独特特性。这两种蛋白质都源自一个共同的祖先。这反映在它们氨基酸序列之间的显著关系、二硫键的高度保守性、内含子-外显子组织以及三维结构上。在研究它们的进化关系时，注意到了一些重要差异，例如，所有α-乳白蛋白都能强烈结合Ca(II)，但只有一些c型溶菌酶能做到。这些特性为未来的研究指明了方向，在对它们的进化历史得出确凿结论之前，这些研究是必要的。
