Kawai Y, Whitsel C, Arinze I J
J Cyclic Nucleotide Protein Phosphor Res. 1986;11(4):265-74.
[32P]ADP-ribosylation of membrane proteins catalyzed by either cholera toxin or pertussis toxin was markedly enhanced by NADP+. The effect was concentration dependent; with 20 microM [32P]NAD+ as a substrate maximal enhancement was obtained at a concentration of 0.5-1.0 mM NADP+ for rabbit and guinea-pig liver membranes and 0.1 mM NADP+ for human erythrocyte membranes. NADP+ appears to act by inhibiting the degradation of NAD+ by NAD+-glycohydrolase (NADase) present in membrane preparations, probably as an alternate substrate for the enzyme. Among inhibitors tested (NADP+, isonicotinic acid hydrazide, imidazole, nicotinamide, L-arginine methyl ester and HgCl2) to suppress the enzyme activity, NADP+ was the most effective and, at 10 mM, inhibited hepatic NADase activity by about 90%. The effect of NADP+ was much greater than that of other known effectors of ADP-ribosylation such as Mg2+ and phosphate, or the NADase inhibitors, isonicotinic acid hydrazide and isonicotinamide. In membranes which contain substantial activities of NADase the inclusion of NADP+ in the assay system is necessary to achieve maximal ADP-ribosylation of membrane proteins.
烟酰胺腺嘌呤二核苷酸磷酸（NADP⁺）可显著增强霍乱毒素或百日咳毒素催化的膜蛋白[³²P] ADP核糖基化作用。该效应呈浓度依赖性；以20微摩尔[³²P]烟酰胺腺嘌呤二核苷酸（NAD⁺）作为底物时，对于兔和豚鼠肝膜，在0.5 - 1.0毫摩尔NADP⁺浓度下可获得最大增强效果，而对于人红细胞膜，在0.1毫摩尔NADP⁺浓度下可获得最大增强效果。NADP⁺似乎通过抑制膜制剂中存在的NAD⁺ - 糖水解酶（NADase）对NAD⁺的降解来发挥作用，可能作为该酶的替代底物。在所测试的用于抑制酶活性的抑制剂（NADP⁺、异烟肼、咪唑、烟酰胺、L - 精氨酸甲酯和氯化汞）中，NADP⁺最为有效，在10毫摩尔时可抑制肝脏NADase活性约90%。NADP⁺的作用远大于其他已知的ADP核糖基化效应物，如镁离子（Mg²⁺）和磷酸盐，或NADase抑制剂异烟肼和异烟酰胺。在含有大量NADase活性的膜中，在测定系统中加入NADP⁺对于实现膜蛋白的最大ADP核糖基化是必要的。
