Guinea pig pancreatic lipase-related protein 2 (GPLRP2) is an interesting model enzyme that can hydrolyze a large set of acylglycerols in vitro but displays however some selectivity depending on the supramolecular structure of substrate and the presence of surfactants like bile salts. We showed that GPLRP2 hydrolyzes 1,2-dipalmitoyl phosphatidylcholine (DPPC) present in mixed micelles with sodium taurodeoxycholate (NaTDC) but not in multilamellar (MLV) and large unilamellar (LUV) vesicles of DPPC. After characterization of these lipid aggregates by dynamic light scattering (DLS), the discriminative recognition of DPPC in DPPC/NaTDC micelles versus MLV and LUV by an inactive variant (S152G) of GPLRP2 to avoid the effect of substrate hydrolysis was investigated using Fourier transform infrared spectroscopy (FTIR). IR spectra were recorded after hydrogen/deuterium exchange, at pD 6 and various temperatures to study phase transitions. We analyzed the methylene asymmetric stretching (ν(CH2)_as), the carbonyl stretching (ν(CO)) and the composite polar head-group vibration bands, first to characterized differences in DPPC micelles and vesicles, and second to estimate the degree of interaction of GPLRP2 S152G with phospholipid. Our results indicate that a significant interaction between GPLRP2 S152G and DPPC is only observed when NaTDC is added to the system to form micelles and this can be explained by the different organization of DPPC in mixed micelles compared to lamellar vesicles (higher hydration of polar head, higher mobility of alkyl chains) that favors GPLRP2 penetration into the phospholipid layer.

豚鼠胰腺脂肪酶相关蛋白2（GPLRP2）是一种有趣的模型酶，可以在体外水解大量的酰基甘油但根据底物的超分子结构和表面活性剂（如胆盐）的存在，显示出一定的选择性。我们表明，GPLRP2水解与牛磺脱氧胆酸钠（NaTDC）混合的胶束中存在的1,2-二棕榈酰磷脂酰胆碱（DPPC），但不会水解DPPC的多层（MLV）和大单层（LUV）囊泡中。通过动态光散射（DLS）对这些脂质聚集体进行表征后，使用傅立叶变换红外光谱技术研究了通过GPLRP2的非活性变体（S152G）区分DPPC / NaTDC胶束中的DPPC与MLV和LUV的区别识别，从而避免了底物水解的影响光谱学（FTIR）。氢/氘交换后，pD 6和各种温度下记录红外光谱，以研究相变。我们分析了亚甲基不对称拉伸ν（CH2）_as），羰基拉伸（ν（CO））和复合极性头基振动带，首先表征DPPC胶束和囊泡中的差异，其次评估GPLRP2 S152G与磷脂的相互作用程度。我们的结果表明，仅当将NaTDC添加到系统中形成胶束时，才能观察到GPLRP2 S152G与DPPC之间的显着相互作用，这可以通过与层状囊泡相比，混合胶束中DPPC的不同组织来解释（极性头的水合度更高，较高的烷基链迁移率），有利于GPLRP2渗透到磷脂层中。