Determination of base composition of DNA by high performance liquid chromatography of its nuclease P1 hydrolysate

The base composition of DNA was directly determined by high performance liquid chromatography (HPLC) of its nuclease P1 hydrolysate. This method can satisfactorily be employed even if the sample of DNA contains RNA or the amount of the sample is very small.     

Differential expression of fucosyl GM1 and a disialoganglioside with a NeuAc alpha 2-6GalNAc linkage (GD1e) in various rat ascites hepatoma cells

A distinct difference in ganglioside composition among various rat ascites hepatomas and Yoshida sarcoma was observed on TLC-immunostaining with anti-fucosyl GM1 antibody, and chemical and enzymatic analyses. Yoshida sarcoma and ascites hepatomas, AH13, AH66F and AH66, but not the other 9 tumor cell lines investigated, specifically contained a disialoganglioside, NeuAc alpha 2-3Gal beta 1-3(NeuAc alpha 2-6)GalNAc beta 1-4Gal beta 1-4Glc beta 1-1ceramide (GD1e), whereas the 9 ascites hepatoma cells without GD1e contained fucosyl GM1. The differential expression of fucosyl GM1 and GD1e in various tumor cell lines indicates that different cell lineages express distinct metabolic pathways for gangliosides, and that the gangliosides are useful markers for distinguishing tumor cell lines.     

Aspartate aminotransferase isozymes from rabbit liver. Purification and properties

Cytosolic and mitochondrial isozymes of aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase [EC 2.6.1.1] ) were purified to homogeneity from rabbit liver. The rabbit liver isozymes were closely similar to the corresponding isozymes from other sources, including human heart, pig heart, chicken heart, and rat liver, in their molecular weights, absorption spectra, amino acid compositions, isoelectric points, and Michaelis constants for the substrates. The NH2-terminal amino acid sequences of rabbit liver isozymes were identified up to 30 residues, and showed some differences from those of the corresponding isozymes obtained from other animals so far studied.     

Purification and characterization of rat brain prostaglandin D synthetase

Prostaglandin D synthetase was purified 2,600-fold from rat brain to apparent homogeneity, as judged by polyacrylamide gel electrophoresis and ultracentrifugation. The purified enzyme was a monomeric protein with a molecular weight of 27,000 +/- 1,000. The pI value, sedimentation coefficient, and partial specific volume were 4.6, 4.1 s, and 0.73 ml/g, respectively. The enzyme was stable between pH 4 and 11 at the temperature lower than 25 degrees C and resistant to a heat treatment under alkaline conditions (pH 8-11). About 50% of the activity was detected after a heat treatment at 100 degrees C for 5 min at pH 10. However, the enzyme was readily inactivated by the isomerase reaction of prostaglandin H2 to prostaglandin D2. The enzyme required sulfhydryl compounds such as dithiothreitol, glutathione, beta-mercaptoethanol, cysteine, and cysteamine for the reaction, but stoichiometric oxidation of these sulfhydryl compounds was not observed. The optimum pH, Km value for prostaglandin H2, and the turnover number were 9.5, 14 microM, and 170 min-1, respectively. The antibody was raised against the purified enzyme in a rabbit, which showed only one positive band in immunoblotting after gel electrophoresis of crude extracts of the brain at the same position as that of the purified enzyme. More than 90% of the prostaglandin D synthetase activity in the brain was absorbed by an excess amount of the antibody, indicating that our preparation is a major component of the enzyme responsible for the biosynthesis of prostaglandin D2 in the brain.     

Mammalian signal peptidase: partial purification and general characterization of the signal peptidase from microsomal membranes of porcine pancreas

Signal peptidase has been enriched extensively from microsomal membranes of porcine pancreas. Microsomal membranes were washed with 1 M KCl and Brij 35, and then solubilized with 1% Nonidet P-40. The solubilized signal peptidase was purified by DEAE-cellulose chromatography and Sepharose CL-6B filtration. Cleavage of pre-human placental lactogen with the partially purified enzyme gave the mature form, whose NH2-terminus was identified as valine. The signal peptidase is heat-labile and approximately 90% of the enzymatic activity was lost at 60 degrees C within 1 min. The pH optimum of the activity was 7 to 8. Chymostatin and o-phenanthroline at concentrations of 2.5 mM inhibited the signal peptidase activity by 62% and 30%, respectively.