Tashiro J, Kobayashi J, Shirai K, Morisaki N, Saito Y
Second Department of Internal Medicine, School of Medicine, Chiba University, Japan.
Scand J Clin Lab Invest. 1999 Apr;59(2):71-6. doi: 10.1080/00365519950185779.
The role of sialic acid linked with lipoprotein lipase (LPL) in its catalytic activity was studied. When LPL was treated with sialidase, the molecular weight decreased by 2000. The sialidase-treated LPL showed unchanged hydrolyzing activity for tributyrin, a water-soluble substrate of esterase, compared with the untreated LPL. The sialidase-treated LPL also showed similar hydrolyzing activity for triolein emulsified with Triton X-100, phosphatidylcholine and phosphatidylethanolamine, whereas it showed significantly increased hydrolyzing activity for triolein emulsified with phosphatidylserine and cardiolipin (152% and 183%, compared with untreated LPL, respectively). In addition, the sialidase-treated LPL showed significantly increased hydrolyzing activity against triolein incorporated into very low-density lipoproteins and chylomicrons (151% and 186%, compared with the untreated LPL, respectively). These results suggest that the loss of sialic acids does not modify the function of the catalytic site of LPL, but facilitates the interaction of the enzyme with the interface of the surface of substrate lipoproteins.
研究了与脂蛋白脂肪酶（LPL）相连的唾液酸在其催化活性中的作用。用唾液酸酶处理LPL后，分子量降低了2000。与未处理的LPL相比，经唾液酸酶处理的LPL对丁酸甘油酯（一种酯酶的水溶性底物）的水解活性未发生变化。经唾液酸酶处理的LPL对用Triton X - 100、磷脂酰胆碱和磷脂酰乙醇胺乳化的三油酸甘油酯也表现出相似的水解活性，而对用磷脂酰丝氨酸和心磷脂乳化的三油酸甘油酯，其水解活性则显著增加（分别比未处理的LPL高152%和183%）。此外，经唾液酸酶处理的LPL对掺入极低密度脂蛋白和乳糜微粒中的三油酸甘油酯的水解活性也显著增加（分别比未处理的LPL高151%和186%）。这些结果表明，唾液酸的缺失不会改变LPL催化位点的功能，但会促进该酶与底物脂蛋白表面界面的相互作用。
