The interaction of pancreatic lipase-related protein 2 (PLRP2) with various micelles containing phospholipids was investigated using pHstat enzyme activity measurements, differential light scattering, size exclusion chromatography (SEC) and transmission IR spectroscopy. Various micelles of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and lysophosphatidylcholine were prepared with either bile salts (sodium taurodeoxycholate or glycodeoxycholate) or Triton X-100, which are substrate-dispersing agents commonly used for measuring phospholipase activities. PLRP2 displayed a high activity on all phospholipid-bile salt micelles, but was totally inactive on phospholipid-Triton X-100 micelles. These findings clearly differentiate PLRP2 from secreted pancreatic phospholipase A2 which is highly active on both types of micelles. Using an inactive variant of PLRP2, SEC experiments allowed identifying two populations of PLRP2-DPPC-bile salt complexes corresponding to a high molecular weight 1:1 PLRP2-micelle association and to a low molecular weight association of PLRP2 with few monomers of DPPC/bile salts. IR spectroscopy analysis showed how DPPC-bile salt micelles differ from DPPC-Triton X-100 micelles by a higher fluidity of acyl chains and higher hydration/H-bonding of the interfacial carbonyl region. The presence of bile salts allowed observing changes in the IR spectrum of DPPC upon addition of PLRP2 (higher rigidity of acyl chains, dehydration of the interfacial carbonyl region), while no change was observed with Triton X-100. The differences between these surfactants and their impact on substrate recognition by PLRP2 are discussed, as well as the mechanism by which high and low molecular weight PLRP2-DPPC-bile salt complexes may be involved in the overall process of DPPC hydrolysis.

胰腺脂肪酶相关蛋白2（PLRP2）与各种含磷脂的胶束的相互作用进行了研究，使用pHstat酶活性测量，差示光散射，尺寸排阻色谱（SEC）和透射红外光谱。1,2-二棕榈酰-sn的各种胶束用胆汁盐（牛磺脱氧胆酸钠或糖脱氧胆酸盐）或Triton X-100（通常用于测量磷脂酶活性的底物分散剂）制备β-甘油-3-磷酸胆碱（DPPC）和溶血磷脂酰胆碱。PLRP2在所有磷脂-胆盐盐胶束中均显示出高活性，但对磷脂-Triton X-100胶束完全无活性。这些发现清楚地将PLRP2与分泌的胰磷脂酶A2区分，后者对两种胶束都具有高活性。使用PLRP2的非活性变体，SEC实验允许鉴定两个群体的PLRP2-DPPC-胆盐复合物，其对应于PLRP2的高分子量1：1胶束缔合和低分子量的PLRP2与DPPC /胆汁的单体缔合盐。红外光谱分析表明，DPPC胆汁盐胶束与DPPC-Triton X-100胶束的不同之处在于酰基链的流动性更高以及界面羰基区域的水合/ H键更高。胆汁盐的存在使观察到添加PLRP2后DPPC的IR光谱发生变化（酰基链的刚性更高，界面羰基区域脱水），而Triton X-100没有观察到变化。讨论了这些表面活性剂之间的差异及其对PLRP2识别底物的影响，以及高分子量和低分子量PLRP2-DPPC-胆盐配合物可能参与DPPC水解的整个过程的机理。胆汁盐的存在使观察到添加PLRP2后DPPC的IR光谱发生变化（酰基链的刚性更高，界面羰基区域脱水），而Triton X-100没有观察到变化。讨论了这些表面活性剂之间的差异及其对PLRP2识别底物的影响，以及高分子量和低分子量PLRP2-DPPC-胆盐配合物可能参与DPPC水解的整个过程的机理。胆汁盐的存在使观察到添加PLRP2后DPPC的IR光谱发生变化（酰基链的刚性更高，界面羰基区域脱水），而Triton X-100没有观察到变化。讨论了这些表面活性剂之间的差异及其对PLRP2识别底物的影响，以及高分子量和低分子量PLRP2-DPPC-胆盐配合物可能参与DPPC水解的整个过程的机理。