Synthesis of nucleoside diphosphates and triphosphates by a salmon milt enzyme preparation

A cell-free enzyme preparation capable of forming nucleoside (or deoxynucleoside) di- and tri-phosphates from the corresponding nucleoside monophosphates in the presence of adenosine triphosphate (ATP) was prepared from immature salmon milts. The preparation was not free from phosphatase activities. The corresponding nucleoside (or deoxynucleoside) di- and tri-phosphates were readily formed from cytidine monophosphate, adenosine monophosphate, uridine monophosphate, and deoxyuridine monophosphate; guanosine monophosphate, deoxycytidine monophosphate, inosine monophosphate, and deoxyribosylthymine monophosphate were poorer substrates. The reaction required ATP. Guanosine triphosphate, uridine triphosphate, cytidine triphosphate, deoxyribosylthymine triphosphate, and inosine triphosphate could replace ATP, though they were in general less effective. With cytidine monophosphate as substrate, the formation of cytidine triphosphate was accelerated by Mg++, Ca++, Mn++, Co++, Ni++, and CN−, and was inhibited by Cu++, Ag+, Zn++, Hg++, F−, iodoacetate, p-hydroxymercuribenzoate, and ethylenediaminetetraacetate. Neither glutathione nor 2-mercaptoethanol in concentrations of between 1 × 10−3 and 1 × 10−1 M protected the enzyme. The optimum pH was 7.5–8.0. The enzyme was very unstable, losing two-thirds of its activity in 1 hour at 30 °C. Under optimum conditions with cytidine monophosphate as substrate, 8.5 μmoles of cytidine triphosphate were formed per hour per milligram of protein nitrogen at 25 °C.

THE REACTION OF SULFONYLIMIDO INTERMEDIATES WITH AROMATIC COMPOUNDS

Thermolysis of methanesulfonyl azide in aromatic solvents gives methanesulfonamide and the isomeric methanesulfonanilides. The orientation of the latter and the relative reactivities of the aromatic substrate towards attack by the methylsulfonylimido intermediate have been studied quantitatively. The high reactivity and also great selectivity of the attacking species are interpreted in terms of a rate-determining addition process to give a sulfonylaziridine derivative followed by a product-determining ring opening and rearrangement to the substituted anilides. Partial rate factors are discussed, as are possible mechanisms for the formation of the methanesulfonamide. The methanesulfonylimido intermediate must be abstracting two hydrogen atoms synchronously from the aromatic substrate.