Lysozyme (LYZ) c‐like proteins are primarily present in the testis and epididymis of male reproductive tissues. Here, we report a novel member of the c‐type LYZ family, the seminal vesicle‐secreted LYZ c‐like protein (SVLLP). Three forms of SVLLP were purified from mouse seminal vesicle secretions and characterized as glycoproteins with the same protein core but different N‐linked glycans. SVLLP is structurally similar to c‐type LYZ proteins. Only one of the 20 invariant residues was altered in the consensus sequence of c‐type LYZs; however, the changed residue (N53S) is one of two essential catalytic residues. LYZ activity assays demonstrated that the three glycoforms of SVLLP lacked enzyme activity. SVLLP is primarily expressed in seminal vesicles. Immunohistochemistry revealed that it occurs in the luminal fluid and mucosal epithelium of the seminal vesicles. Testosterone is not the primary regulator for its expression in the seminal vesicle. SVLLP binds to sperm and suppresses bovine serum albumin‐induced sperm capacitation, inhibits the acrosome reaction, and blocks sperm–oocyte interactions in vitro, suggesting that SVLLP is a sperm capacitation inhibitor.

中文翻译：

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小鼠精囊分泌的溶菌酶 c 样蛋白调节精子获能

溶菌酶 (LYZ) c 样蛋白主要存在于男性生殖组织的睾丸和附睾中。在这里，我们报告了 c 型 LYZ 家族的一个新成员，精囊分泌的 LYZ c 样蛋白（SVLLP）。从小鼠精囊分泌物中纯化出三种形式的 SVLLP，并表征为具有相同蛋白质核心但不同 N-连接聚糖的糖蛋白。SVLLP 在结构上类似于 c 型 LYZ 蛋白。在 c 型 LYZ 的共有序列中，只有 20 个不变残基中的一个发生了改变；然而，变化的残基 (N53S) 是两个必不可少的催化残基之一。LYZ 活性测定表明 SVLLP 的三种糖型缺乏酶活性。SVLLP 主要在精囊中表达。免疫组织化学显示它发生在精囊的腔液和粘膜上皮中。睾酮不是其在精囊中表达的主要调节剂。SVLLP 与精子结合并抑制牛血清白蛋白诱导的精子获能，抑制顶体反应，并在体外阻断精子-卵母细胞相互作用，表明 SVLLP 是精子获能抑制剂。