The nature of the inhibition of Ehrlich tumor cell ribonucleotide reducÃ-ase by combinations of agents directed at the nonheme iron-containing component and the effector-binding com ponent was studied with the use of isobolograms. From these studies, it was determined that the combinations of pyrazoloimidazole (IMPY) and dialdehyde of inosine, IMPY and deoxyguanosine triphosphate (dGTP), IMPY a...

Ca2+ and GTP are the main modulators of type-2 transglutaminases. To study the interaction of the enzyme with GTP, we have employed periodate-oxidized GTP as an affinity-label probe. Dialdehyde GTP bound irreversibly to type-2 transglutaminase in a time-dependent way with 1:1 stoichiometry at complete modification. The reaction took place in the absence, but was more rapid in the presence, of c...

Past studies have suggested that mouse sperm surface galactosyltransferase may participate during fertilization by binding N-acetylglucosamine (GlcNAc) residues in the zona pellucida. In this paper, we examined further the role of sperm surface galactosyltransferase in mouse fertilization. Two reagents that specifically perturb sperm surface galactosyltransferase activity both inhibit sperm-zon...

Homogeneous Escherichia coli methionyl-, isoleucyl-, tryptophanyl-, and phenylalanyl-tRNA synthetases and Bacillus stearothermophilus methionyl- and tyrosyl-tRNA synthetases are irreversibly inactivated by reaction of their active ATP sites with the 2',3'-dialdehyde derivative of ATP obtained by periodate oxidation. In each case, the amount of 14C-labeled dialdehyde derivative incorporated per ...

The nature of the inhibition of Ehrlich tumor cell ribonucleotide reductase by combinations of agents directed at the non-heme iron-containing component and the effector-binding component was studied with the use of isobolograms. From these studies, it was determined that the combinations of pyrazoloimidazole (IMPY) and dialdehyde of inosine, IMPY and deoxyguanosine triphosphate (dGTP), IMPY an...

As theophylline is known to stimulate lipolysis and lipid mobilisation, plasma concentrations of malonyl dialdehyde were studied in asthmatic patients being treated with sustained release theophylline. Malonyl dialdehyde was assessed as malonyl dialdehyde like material (MDA-LM) by the thiobarbituric acid assay. In a kinetic study (eight patients) plasma MDA-LM concentrations were found to be si...

Adenosine dialdehyde and nitrous oxide, specific S-adeno-sylhomocysteine hydrolase and methionine synthetase inhibitors, respectively, induced differentiation of the human promyelocytic cell line HL-60. Their effect did not appear to be mediated through changes in transmethylation or decreased S-adenosylmethionine synthesis because (1) there was little correlation between the concentrations of ...

Plasma membrane-enriched fractions were obtained from the Balb/c 3T12 cell line by a conventional technique. The specific activities of two plasma membrane markers, 5’-nucleotidase and (Na+-K+)-ATPase were enriched loto l&fold and 6to lo-fold, respectively, over homogenates in these preparations. Galactosyltransferase activity toward N-acetylglucosamine and asialo-agalacto-fetuin was associated...

This critique points out that a number of possible alterations in cell metabolism could lead to changes in membrane structure and that the observed effects might not necessarily play a primary role in the physiology of aging. Experimental approaches, while not simple, should distinguish causes of altered membrane asymmetry from its consequences. THE idea that cross-linking agents might play a r...