The manganese-enzyme-substrate complexes of a number of nucleoside diphosphate substrates of creatine kinase showed a range of enhanced values of the longitudinal proton relaxation rate of water with respect to the manganous aquocation, although the small enhancement factors, ca, of all the binary manganese-nucleotide complexes were the same, approximately 1.6. The order of the values of t, the...

Ribonucleotide reductase (RNR) is an essential enzyme for the de novo synthesis of both cellular and viral DNA and catalyzes the conversion of ribonucleoside diphosphates into the corresponding deoxyribonucleoside diphosphates. The enzyme consists of two nonidentical subunits, termed R1 and R2, whose expression is very low in resting cells and maximal in S-phase cells. Here we show that murine ...

In considering how a complex polynucleotide such as DNA1 is assembled by a cell, the authors were guided by the known enzymatic mechanisms for the synthesis of the simplest of the nucleotide derivatives, the coenzymes. The latter, whether composed of an adenosine, uridine, guanosine, or cytidine nucleotide, are formed by a nucleotidyl transfer from a nucleoside triphosphate to the phosphate est...

Ribonucleoside diphosphates react to form polyribonucleotides and inorganic phosphate. Studies of the nature of nucleotide incorporation into nucleic acid in Escherichia coli led to the recognition of a similar reaction by Littauer and Kornberg (3). Beers (4,5) and Olmsted (6,7) have investigated the phosphorylase in Micrococcus lysodeikticus. Heppel et al. (8-10) have elucidated the structure ...

Levosimendan, a new Ca++-sensitizing and positive inotropic agent, was reported to act as a coronary vasodilator and protect ischemic myocardium. To elucidate the mechanisms of these actions, the possible electrophysiological effects of levosimendan on isolated rat ventricular cells were examined by the patch-clamp technique with whole-cell and single-channel recordings. Levosimendan (3 and 10 ...

In considering how a complex polynucleotide such as DNA1 is assembled by a cell, the authors were guided by the known enzymatic mechanisms for the synthesis of the simplest of the nucleotide derivatives, the coenzymes. The latter, whether composed of an adenosine, uridine, guanosine, or cytidine nucleotide, are formed by a nucleotidyl transfer from a nucleoside triphosphate to the phosphate est...

The sulfate-dependent pyrophosphate exchange reaction has been re-examined and confirmed. Standard assay conditions for measuring ATP sulfurylase by sulfate-dependent pyrophosphate exchange are described and some properties of the enzyme (measured in crude dialyzed extracts) are reported. This method has many advantages over the well established molybdate method.