Iwaki M, Ogiso T, Inagawa S, Kakehi K
Faculty of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502,
J Pharm Sci. 1999 Jan;88(1):52-7. doi: 10.1021/js9802704.
beta-1-O- (NAG) and 2-O-glucuronides (2-isomer) of (S)-naproxen (NA) were prepared to determine which positional isomer(s) of the acyl glucuronide of NA is responsible for forming covalent adducts with human serum albumin (HSA). Their comparative stability and covalent binding adduct formation with HSA were investigated at pH 7.4 and at 37 degreesC. NA and its acyl glucuronides were simultaneously determined by HPLC. Three positional isomers were formed successively after incubation of NAG in the buffer only. However, when NAG was incubated with HSA (30 mg/mL), isomers other than the 2-isomer were formed in little or negligible quantities. In HSA solution, NAG (kd = 2.08 +/- 0.08 h-1) was four times less stable than 2-isomer (kd = 0.51 +/- 0.02 h-1). NAG was degraded by hydrolysis (khyd = 1.01 +/- 0.10 h-1) and isomerization (kiso = 1.07 +/- 0.07 h-1) to the same extent; however, hydrolysis was predominant for the 2-isomer (kd = 0.51 +/- 0.02 h-1). The incubation of both NAG and 2-isomer with HSA led to the formation of a covalent adduct; however, the adduct formation from the 2-isomer proceeded more slowly than that from NAG. The present results suggest that the covalent binding of NA to HSA via its acyl glucuronides proceeds through both transacylation (direct nucleophilic displacement) and glycation mechanisms; NAG rapidly forms an adduct that may be unstable, and the protein adduct from the 2-O-acyl glucuronide is as important for the covalent binding as those from the 1-O-acyl glucuronides.
制备了（S）-萘普生（NA）的β-1-O-（N-乙酰葡糖胺）和2-O-葡糖醛酸苷（2-异构体），以确定NA的酰基葡糖醛酸的哪些位置异构体负责与人血清白蛋白（HSA）形成共价加合物。在pH 7.4和37℃下研究了它们与HSA的相对稳定性和共价结合加合物的形成。通过高效液相色谱法同时测定NA及其酰基葡糖醛酸苷。仅在缓冲液中孵育N-乙酰葡糖胺后，依次形成了三种位置异构体。然而，当N-乙酰葡糖胺与HSA（30 mg/mL）一起孵育时，除2-异构体以外的异构体形成的量很少或可忽略不计。在HSA溶液中，N-乙酰葡糖胺（kd = 2.08±0.08 h-1）的稳定性比2-异构体（kd = 0.51±0.02 h-1）低四倍。N-乙酰葡糖胺通过水解（khyd = 1.01±0.10 h-1）和异构化（kiso = 1.07±0.07 h-1）降解的程度相同；然而，对于2-异构体（kd = 0.51±0.02 h-1），水解占主导。N-乙酰葡糖胺和2-异构体与HSA的孵育均导致形成共价加合物；然而，2-异构体形成加合物的过程比N-乙酰葡糖胺的过程进行得更慢。目前的结果表明，NA通过其酰基葡糖醛酸与HSA的共价结合通过转酰基作用（直接亲核取代）和糖基化机制进行；N-乙酰葡糖胺迅速形成可能不稳定的加合物，并且来自2-O-酰基葡糖醛酸的蛋白质加合物对于共价结合与来自1-O-酰基葡糖醛酸苷的加合物同样重要。
