[理学]酶的分子修饰background.ppt

1990年Goodson将干扰素的Thr3替换为Cys3，并通过PEG修饰，水溶性增加，半衰期延长(工程二硫键 ) 噬菌体T4溶菌酶Ile3突变为Cys3，使与Cys97形成二硫键，催化活性不变，但热稳定性显著提高(工程二硫键) xylanase(工程二硫键) used to treat wood pulp in paper production needs to function at high temp Glu49位于色氨酸合成酶的疏水核心部分。如Ala取代，稳定性增加(增加蛋白质内部疏水性) PEGylated microspheres: Li et al. showed significant increases in circulation time by preparing controlled release microparticles using PEG-PLGA block copolymers ? Block copolymer self-emulsifies and PEG coats both internal and external aqueous interfaces ? Benefit of improved protein stability within microspheres? Block copolymer localizes at aqueous/polymer interfaces ?? Unmodified PLGA particles t1/2 = 13.6 min. ?? PEG block copolymer particles t1/2 = 270 min (4.5 hr) ?? Altered biodistribution: high blood availability and reduced spleen/liver uptake No PLGA particles remaining in blood after 12 hrs Harris, J. M. Chess, R. B. Effect of pegylation on pharmaceuticals. Nat Rev Drug Discov 2, 214-21 (2003). 重组白介素（rIL-2）用大分子PEG修饰后，半衰期延长10倍 腺苷脱氨酶（ADA） 用于治疗联合免疫缺陷 PEG修饰的ADA在体内的半衰期从数分钟延长到24小 时，免疫原性降低 1990年美国食品和药品管理局（FDA）批准用于联合免疫缺陷的治疗 天冬酰胺酶（ASP） 用于白血病的治疗 PEG修饰后半衰期从24小时增加到357小时 FDA1994年批准用于急性淋巴细胞性白血病治疗 IFN-α –2a PEG修饰后疗效增加 FDA已批准正式生产，如Roche公司的PEGASYSTM Peg-Interferon-2a Pegasys? (Roche) Hepatitis C (2000) IFN-α –2b PEG修饰后半衰期延长5倍 Schering-Plough公司的Peg-Intron Peg-Interferon-2b PEG-Intron A? (Schering) Hepatitis C (2001) Protein-Polymer Bioconjugates Interferon-a-2a (IFN-a-2a) Conjugated IFN-a-2a Commercially available Activated PEG Disadvantages of IFN treatment Side effects common Expensive Effective in only minority of chronic HBV infection patients Pegylated IFNa Pegylation = the addition of an inert polyethylene glycol (PEG) to a protein molecule increasing its molecular weight without affecting its therapeutic activity 2 main effects of pegylation of IFNa longer lasting therapeutic effect reducing immunogenicity potential Peg in