RESUMO
A homogeneous preparation of EF-2 from Guerin tumour cells was obtained. Its Mr (68 000), pI (6.5), optimum pH (7.0) and amino acid composition are very close to those of rat liver elongation factor. EF-2 from Guerin tumour cells is active in the heterologous liver - tumour system, although half as effective as in the homologous system.
Assuntos
Neoplasias Experimentais/análise , Fatores de Alongamento de Peptídeos/isolamento & purificação , Aminoácidos/análise , Animais , Fígado/análise , Peso Molecular , Fator 2 de Elongação de Peptídeos , Fatores de Alongamento de Peptídeos/metabolismo , RatosRESUMO
UDP-D-[U-14C]galactose is decomposed to [U-14C]galactose-1-phosphate and [U-14C]galactose by rat liver microsomal and crude polyribosomal fractions, under conditions commonly used to assay of glycosyltransferase activities. UDP-D-[U-14C]galactose, at neutral pH, is also chemically degraded to the [U-14C]galactose-1,2-cyclic phosphate. The 1,2-cyclic phosphate derivative of galactose also exists in the commercial UDP-D-[U-14C]galactose. It is a very important finding that products of the UDP-D-[U-14C]galactose decomposition are tightly, although nonenzymatically, bound to tested subcellular fractions and may create a false impression of protein glycosylation. The application of controls containing all radioactive substances present in suitable samples is recommended in order to avoid incorrect interpretations of the results.
Assuntos
Microssomos Hepáticos/metabolismo , Polirribossomos/metabolismo , Uridina Difosfato Galactose/metabolismo , Açúcares de Uridina Difosfato/metabolismo , Animais , Radioisótopos de Carbono , Galactose/metabolismo , Galactosefosfatos/metabolismo , Glicoproteínas/biossíntese , Glicosilação , Técnicas In Vitro , RatosRESUMO
The binding of UDP-N-acetylhexosamines with purified ribosomes was studied and it was found that the radioactive nucleotides can be attached to these particles. The radioactivity of the purified ribosomal pellet depends on the amounts of ribosomes and UDP-N-acetylhexosamines. Some characteristics of the binding system indicate that the attachment of UDP-sugar to ribosome does not require the participation of glycosyltransferases. The results of the competition experiment would suggest that there are specific sites on ribosomes for the binding of UDP-N-acetylglucosamine.
Assuntos
Fígado/metabolismo , Açúcares de Nucleosídeo Difosfato/metabolismo , Ribossomos/metabolismo , Uridina Difosfato N-Acetilglicosamina/metabolismo , Açúcares de Uridina Difosfato/metabolismo , Acetilglucosamina/metabolismo , Animais , Radioisótopos de Carbono , Cinética , Masculino , Ratos , Ratos Endogâmicos , Uridina Difosfato N-Acetilgalactosamina/metabolismoRESUMO
After incubating pieces of human gastric mucous membrane with radioactive galactose, labeled metabolites of glycolysis (FDP,PEP,pyruvate):hexose and hexosamine intermediates in glycoconjugate biosynthesis (gal-1P, UDP-gal,acetylated hexosamines, and their phosphate esters), amino acids (glycine, alanine, and serine), and oxoglutarate as a metabolite of the citric acid cycle were isolated from the acid-soluble fraction. These results suggest that galactose in the human gastric mucous membrane is epimerized to glucose and metabolized in the glycolytic pathway together with oxidation in the citric acid cycle and in the direction of glycoconjugate biosynthesis.
Assuntos
Galactose/metabolismo , Mucosa Gástrica/metabolismo , Cromatografia por Troca Iônica , Cromatografia em Papel , Glucose/biossíntese , Glicólise , Humanos , Concentração de Íons de Hidrogênio , Técnicas In Vitro , Oxirredução , SolubilidadeRESUMO
Pieces of human gastric mucosa were incubated with labeled galactose. The ratio of glucosamine-galactosamine radioactivity in human gastric glycoconjugates, after incubation of the tissue with labeled galactose, was similar to that of the two compounds after incubation with labeled glucose.
Assuntos
Galactose/metabolismo , Mucosa Gástrica/metabolismo , Hexosaminas/metabolismo , Humanos , Hidrólise , Técnicas In Vitro , SolubilidadeRESUMO
A rapid and simple procedure for isolation of 40S and 60S ribosomal subunits by ion-exchange column chromatography is described. The dissociated ribosomes can be separated and non-ribosomal proteins and low-molecular-weight substances removed. An assessment by physicochemical and functional criteria showed that the ribosomal subunits obtained are active and sufficiently homogeneous.