Although information about invertebrate lysozymes is scarce, these enzymes have been described as components of the innate immune system, functioning as antibacterial proteins. Here we describe the first thermodynamic and structural study of a new C-type lysozyme from a Pacific white shrimp Litopenaeus vannamei (LvL), which has shown high activity against both Gram (+) and Gram (−) bacteria including Vibrio sp. that is one of the most severe pathogens in penaeid shrimp aquaculture. Compared with hen egg-white lysozyme, its sequence harbors a seven-residue insertion from amino acid 97 to 103, and a nine-residue extension at the C-terminus only found in penaeid crustaceans, making this enzyme one of the longest lysozyme reported to date. LvL was crystallized in the presence and absence of chitotriose. The former crystallized as a monomer in space group P6₁ and the latter in P2₁2₁2₁ with two monomers in the asymmetric unit. Since the enzyme crystallized at a pH where lysozyme activity is deficient, the ligand could not be observed in the P6₁ structure; therefore, we performed a docking simulation with chitotriose to compare with the hen egg lysozyme crystallized in the presence of the ligand. Remarkably, additional amino acids in LvL caused an increase in the length of α-helix H4 (residues 97–103) that is directly related to ligand recognition. The K_a for chitotriose (4.1 × 10⁵ M⁻¹), as determined by Isothermal Titration Calorimetry, was one order of magnitude higher than those for lysozymes from hen and duck eggs. Our results revealed new interactions of chitiotriose with residues in helix H4.

尽管缺乏关于无脊椎动物溶菌酶的信息，但这些酶已被描述为先天免疫系统的组成部分，具有抗菌蛋白的功能。在这里，我们描述了来自太平洋白对虾凡纳滨对虾（LvL）的新型C型溶菌酶的首次热力学和结构研究，该研究显示对革兰氏（+）和革兰氏（-）细菌（包括弧菌）均具有高活性sp。这是对虾虾养殖中最严重的病原体之一。与鸡蛋清溶菌酶相比，它的序列在氨基酸97至103之间插入了7个残基，在C末端仅在对虾甲壳类动物中发现了9个残基，这使得该酶成为据报道最长的溶菌酶之一。日期。LvL在存在和不存在壳三糖的情况下结晶。前者在空间群P6 _1中结晶为单体，后者在P2 ₁ 2 ₁ 2 _1中结晶，其中两个单体在不对称单元中。由于该酶在溶菌酶活性不足的pH值下结晶，因此无法在P6 _1中观察到配体结构体; 因此，我们用壳三糖进行了对接模拟，以与在配体存在下结晶的鸡蛋溶菌酶进行比较。值得注意的是，LvL中的其他氨基酸导致α-螺旋H4的长度增加（残基97-103），这与配体识别直接相关。通过等温滴定热量法测定的壳三糖（4.1×10 ⁵  M ^-1）的K _a比来自母鸡和鸭蛋的溶菌酶的K _a高一个数量级。我们的结果揭示了壳三糖与螺旋H4中残基的新相互作用。