Product release mechanism of Lipocalin-type Prostaglandin D synthase

Lipocalin型前列腺素D合成酶(L-PGDS)催化前列腺素H2(PGH2)异构化生成前列腺素D2(PGD2)，前列腺素D2是脑内一种强有力的内源性睡眠激素。L-前列腺素DS作为治疗睡眠障碍的药物靶点已有大量研究报道，试图了解其催化机制，并提出了几种L-PGDS的底物识别模型。然而，L-PDGS识别其底物和产物的详细机制尚不清楚，因为L-PGDS与其底物和产物相互作用的基本信息，如其结合亲和力和化学计量比仍不清楚。因此，我们进行了ITC和核磁共振实验来表征其结合性质。红外光谱和核磁共振结果表明，底物和产物均以2：1的化学计量比与L-PGDS结合，并存在两个结合部位，即高亲和力结合部位和低亲和力结合部位。

Lipocalin-type Prostaglandin D synthase (L-PGDS) catalyzes the isomerization of prostaglandin H2 (PGH2) to produce prostaglandin D2 (PGD2), which acts as a potent endogenous somnogen in the brain. A number of studies of L-PGDS, as a drug target for sleep disorders, have been reported in attempts to understand its catalytic mechanism, and several substrate recognition models of L-PGDS have been proposed. However, details of the mechanism by which L-PDGS recognizes its substrates and products are obscure, since essential information, such as its binding affinity and stoichiometry, of the interactions between L-PGDS and its substrates and products remains unclear. Therefore, we carried out ITC and NMR experiments to characterize the binding properties. The results of the ITC and NMR measurements revealed that both the substrate and the product bind to L-PGDS in a stoichiometry of 2 to 1 and two binding sites, namely a high and a low affinity binding site, are present.