Bethea Heather N, Xu Ding, Liu Jian, Pedersen Lars C
Division of Medicinal Chemistry and Natural Products, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA.
Proc Natl Acad Sci U S A. 2008 Dec 2;105(48):18724-9. doi: 10.1073/pnas.0806975105. Epub 2008 Nov 20.
Heparan sulfate (HS) is a polysaccharide involved in essential physiological functions from regulating cell growth to blood coagulation. HS biosynthesis involves multiple specialized sulfotransferases such as 2-O-sulfotransferase (2OST) that transfers the sulfo group to the 2-OH position of iduronic acid (IdoA) or glucuronic acid (GlcA) within HS. Here, we report the homotrimeric crystal structure of 2OST from chicken, in complex with 3'-phosphoadenosine 5'-phosphate. Structural based mutational analysis has identified amino acid residues that are responsible for substrate specificity. The mutant R189A only transferred sulfates to GlcA moieties within the polysaccharide whereas mutants Y94A and H106A preferentially transferred sulfates to IdoA units. Our results demonstrate the feasibility for manipulating the substrate specificity of 2OST to synthesize HS with unique sulfation patterns. This work will aid the development of an enzymatic approach to synthesize heparin-based therapeutics.
硫酸乙酰肝素（HS）是一种多糖，参与从调节细胞生长到血液凝固等重要生理功能。HS生物合成涉及多种特殊的磺基转移酶，如2-O-磺基转移酶（2OST），它将磺基转移到HS中艾杜糖醛酸（IdoA）或葡萄糖醛酸（GlcA）的2-OH位置。在此，我们报道了鸡源2OST与3'-磷酸腺苷5'-磷酸形成复合物的同源三聚体晶体结构。基于结构的突变分析确定了负责底物特异性的氨基酸残基。突变体R189A仅将硫酸盐转移到多糖中的GlcA部分，而突变体Y94A和H106A则优先将硫酸盐转移到IdoA单元。我们的结果证明了操纵2OST的底物特异性以合成具有独特硫酸化模式的HS的可行性。这项工作将有助于开发一种酶促方法来合成基于肝素的治疗药物。
