The resistance of human tumor strains in culture to cell killing by alkylating nitrosoureas is correlated with their levels of the DNA repair activity O6-methylguanine-DNA methyltransferase. Strains with the Mer- phenotype have no activity and are extremely sensitive. However, the relationship between the sensitivity of human tumors in vivo and transferase levels is not known, and even the exis...

1. Transferase I of rat liver binds aminoacyl-tRNA to form a relatively stable complex, which is retained on cellulose nitrate filters. This reaction proceeds at both 0 degrees C and 37 degrees C and is inhibited by GTP. The resulting product is stabilized by GTP and Mg(2+). 2. Only very low quantities of deacylated tRNA are bound by transferase I. 3. Methods are described for the preparative i...

Terminal deoxyribonucleotidyl transferase (EC 2.7.7.31; nucleoside triphosphate:DNA nucleotidylexotransferase) is usually found only in thymus, but has been reported in leukemic cells from children with acute lymphoblastic leukemia. In an unusual adult patient with acute myelomonocytic leukemia, terminal transferase was found at a level of 16 units per 10(8) bone marrow cells and 14 units per 1...

Renal and hepatic GSH (reduced glutathione) S-transferase were compared with respect to substrate and inhibitory kinetics and hormonal influences in vivo. An example of each of five classes of substrates (aryl, aralkyl, epoxide, alkyl and alkene) was used. In the gel filtration of renal or hepatic cytosol, an identical elution volume was found for all the transferase activities. Close correspon...

The effect of enzymatically generated reduced oxygen metabolites on the activity of hepatic microsomal glutathione S-transferase activity was studied to explore possible physiological regulatory mechanisms of the enzyme. Noradrenaline and the microsomal cytochrome P-450-dependent monooxygenase system were used to generate reduced oxygen species. When noradrenaline (greater than 0.1 mM) was incu...

A high molecular weight preparation of terminal transferase containing 58,000- and 44,000-dalton peptides has been purified from calf thymus glands. The relationship of these terminal transferase peptides to the low molecular weight form was established with an immunoblot procedure using rabbit antibody directed against the homogeneous calf thymus low molecular weight terminal transferase (32,0...

Intrigued by similar specificities of the hydra feeding receptor and y-glutamyl transferase activity toward GSH, we examined the possibility that these two GSH-bihding activities might reside in the same protein. We find that the two activities differ in specificity toward the y-glutamyl moiety of GSH. The hydra transferase recognizes L-azaserine, L-Glu, D-Glu and L-Gln. The feeding receptor re...

The association of mutant forms of Ras protein with a variety of human cancers has stimulated intense interest in therapies based on inhibiting oncogenic Ras signaling. Attachment of Ras proteins to the plasma membrane is required for effective Ras signaling and is initiated by the enzyme farnesyl protein transferase. We found that in the presence of potent farnesyl protein transferase inhibito...