Determinants of pH profile and acyl chain selectivity in lysosomal phospholipase A2 [S]
作者:Vania Hinkovska-Galcheva、Robert Kelly、Kelly A. Manthei、Renee Bouley、Wenmin Yuan、Anna Schwendeman、JohnJ.G. Tesmer、James A. Shayman
DOI:10.1194/jlr.m084012
日期:——
Lysosomal phospholipase A2 (LPLA2) is characterized by broad substrate recognition, peak activity at acidic pH, and the transacylation of lipophilic alcohols, especially N-acetyl-sphingosine. Prior structural analysis of LPLA2 revealed the presence of an atypical acidic residue, Asp13, in the otherwise hydrophobic active site cleft. We hypothesized that Asp13 contributed to the pH profile and/or substrate
溶酶体磷脂酶A2(LPLA2)的特征是广泛的底物识别,在酸性pH下具有峰值活性以及亲脂性醇(尤其是N-乙酰基-鞘氨醇)的酰基转移。LPLA2的先前结构分析显示,在否则为疏水活性位点的裂口中存在非典型酸性残基Asp13。我们假设Asp13有助于pH谱和/或LPLA2对不饱和酰基链的底物偏爱。为了验证这一假设,我们用Asp13取代了丙氨酸,半胱氨酸或苯丙氨酸。然后,我们监测了1-O-酰基-N-乙酰基鞘氨醇的形成,以测量各种甘油磷脂上sn-1和sn-2酰基的水解情况。在中性pH值下,用Asp13取代产生显着的酶活性(7。4)并干扰了单不饱和和双不饱和酰基链的选择性。但是,该位置在选择酰基受体或甘油磷脂的头基中没有明显作用。我们的模型表明,Asp13及其取代基通过形成易碎的酰基链所占据的疏水轨道的一部分,有助于LPLA2的pH活性曲线和酰基链选择性。