Denitrosation of nitrosamines—a quantitative study. Reactions of N-methyl-N-nitrosoaniline, N-nitrosoproline, dimethylnitrosamine and N-nitrososarcosine

Peptidyl N-Nitrosoanilines: A Novel Class of Cysteine Protease Inactivators,

“…Nevertheless, in serine proteases, the nucleophilic attack of the active site serine on the substrate amide bond precedes protonation. In cysteine proteases, on the other hand, protonation of the scissile amide bond occurs prior to or concomitant with the nucleophilic attack. 33a,b It has been proposed that, at physiological pH, 90% of the papain exists in a form wherein the active site consists of kinetically effective imidazolium thiolate zwitterionic pair. 33c,d Such initial protonation, a crucial step in the denitrosation of N -nitrosoaniline by a nucleophilic group (Scheme ), is only possible in cysteine proteases due to the existence of a thiolate−imidazolium ion pair in the Michaelis complex and in the free enzyme. On the other hand, despite the higher nucleophilicity of alkoxides than thiolates, initial protonation of N -nitrosoaniline is not feasible in serine proteases since the serine and histidine residues are neutral at the corresponding stages.…”

Transnitrosation of non-mutagenic N-nitrosoproline forms mutagenic N-nitroso-N-methylurea

“…23,[28][29][30][31] Many reports have shown kinetic data obtained by decreasing the initial concentration of starting N-nitrosamines, whereas only a few reports have shown kinetic data obtained by formation of N-nitrosamines 28,29 or S-nitroso compounds 35,36 produced by transnitrosation of N-nitrosamines. Although NMU has been reported to form by nitrosation in vivo, [5][6][7][8] there have been few reports of NMU formation by transnitrosation of non-mutagenic N-nitrosamine.…”

“…Thiocyanate is one of the accelerators for transnitrosation, 21,28,29,31 however, it has been reported to have lower catalytic activity than thioureas. 23,25,27,32 In addition to 1,1,3,3-tetramethylthiourea (TTU) and 1,3-dimethylthiourea (DTU), other sulfur compounds; thioacetamide, cysteine, methionine and glutathione, were tested as possible accelerators for transnitrosation from NP to N-methylurea in this study. NMU was not detected following the reaction with cysteine, methionine and glutathione, and only a trace amount of NMU was detected after 22 h reaction with thioacetamide (data not shown).…”

“…17 Transnitrosation, in which a nitroso group is transferred from nitrosamine to another amine, is a reaction characteristic of N-aryland N-alkyl-N-nitrosoureas, [18][19][20][21] and N-aryl-N-nitrosamines. [22][23][24][25][26][27] Furthermore, transnitrosation by aliphatic nitrosamines under appropriate conditions have also been reported. 23,28-31 Thus a non-carcinogenic N-nitrosamine can give carcinogenic compound by transnitrosation under the acidic conditions of the mammalian stomach.…”

Nitrosamine Reactivity: A Survey of Reactions and Purge Processes

“…Acids studied were strong mineral acids like HCl, H 2 SO 4 , and HClO 4 ; the last two acids were used when nucleophilic additives were being compared. Additives studied included halides, thiourea, and thiocyanate. , After NOY forms, it will rapidly react with the NO traps or additives, depending on the conditions. Nitroso traps studied under acidic conditions were urea, 2,4-dinitroaniline, hydroxylamine, sulfanilic acid, ammonia, sulfanilamide, hydrazine, sulfamic acid, and 4-nitroaniline .…”