De Bisschop H C, De Meerleer W A, Willems J L
Technical Division of the Army, Department for Nuclear, Biological and Chemical Protection, Vilvoorde, Belgium.
Biochem Pharmacol. 1987 Nov 1;36(21):3587-91. doi: 10.1016/0006-2952(87)90006-2.
Phosphonylation has been reported as part of the degradation of soman in human serum. The concentration of phosphonylation sites can be quantified by comparing the degradation in serum, preincubated with soman (all sites occupied), with the degradation in serum not preincubated. The mean value of 73 nM of phosphonylation sites is in agreement with the concentration of active sites of butyrylcholinesterase (EC 3.1.1.8.), which is known to be phosphonylated by soman. Hence, it is concluded that butyrylcholinesterase accounts for all the phosphonylation sites present in human serum. The stereoselectivity of the reaction was investigated by using epimeric pairs of soman, in casu C(+)P(+/-)- and C(-)P(+/-)-soman. In a first approach enzymatic hydrolysis was blocked and the ratios of phosphonylation rate constants, C(+)P(+)/C(+)P(-) and C(-)P(+)/C(-)P(-), were determined to be 0.15 and 0.31, respectively. In a second approach, in untreated serum, the bimolecular phosphonylation rate constants of C(+)P(-)- and C(-)P(-)-soman were determined, neglecting their small hydrolysis rate and taking advantage of the fast enzymatically catalysed disappearance of their respective P(+)-epimeric counterparts. Values for C(+)P(-)- and C(-)P(-)-soman are 3.6 X 10(7) and 0.6 X 10(7) M-1.min-1, respectively. Using a combination of both approaches, a relative ranking of phosphonylation rates of the four isomers was found to be C(+)P(-) much greater than C(+)P(+) approximately equal to C(-)P(-) greater than C(-)P(+).
据报道，膦酰化是梭曼在人血清中降解过程的一部分。通过比较预先与梭曼孵育（所有位点均被占据）的血清中的降解情况与未预先孵育的血清中的降解情况，可以对膦酰化位点的浓度进行定量。膦酰化位点的平均值为73 nM，这与丁酰胆碱酯酶（EC 3.1.1.8.）的活性位点浓度一致，已知该酶会被梭曼膦酰化。因此，可以得出结论，丁酰胆碱酯酶是人类血清中所有膦酰化位点的来源。通过使用梭曼的差向异构体对，即C(+)P(+/-)-和C(-)P(+/-)-梭曼，研究了该反应的立体选择性。在第一种方法中，酶促水解被阻断，膦酰化速率常数的比值，即C(+)P(+)/C(+)P(-)和C(-)P(+)/C(-)P(-)，分别测定为0.15和0.31。在第二种方法中，在未处理的血清中，测定了C(+)P(-)-和C(-)P(-)-梭曼的双分子膦酰化速率常数，忽略了它们较小的水解速率，并利用它们各自的P(+)-差向异构体对应物在酶促催化下的快速消失。C(+)P(-)-和C(-)P(-)-梭曼的值分别为3.6×10(7)和0.6×10(7) M-1·min-1。结合这两种方法，发现四种异构体的膦酰化速率的相对排序为C(+)P(-)远大于C(+)P(+)约等于C(-)P(-)大于C(-)P(+)。
