RESUMO
Isoform patterns of six lysosomal glycosidases were studied in leukemic lymphoid cells phenotypically related to B and T cells at distinct stages of differentiation. In all types of cells, the activity of glycosidases under study was expressed in two major isoforms. No correlation was observed between isoform patterns and cell phenotypes. The beta-hexosaminidase isoform ratios for phenotypically related leukemic lymphoid cells but isolated from different sources (blood and spleen) differed. It was suggested that cell localization affects isoform expression. An anomalous alpha-mannosidase was detected in lymphoid cells from lymph nodes, while it was lacking in the phenotypically related blood lymphoid cells from the same patients. Isoform I of beta-hexosaminidase was recorded in lymphoid cells of patients with anemias.
Assuntos
Anemia/enzimologia , Linfócitos B/imunologia , Glicosídeo Hidrolases/análise , Isoenzimas/análise , Leucemia/enzimologia , Tecido Linfoide/enzimologia , Linfoma/enzimologia , Lisossomos/enzimologia , Linfócitos T/imunologia , Antígenos CD/análise , Glucuronidase/análise , Humanos , Linfonodos/enzimologia , Manosidases/análise , Fenótipo , Síndrome de Sézary/enzimologia , Baço/enzimologia , alfa-Manosidase , beta-N-Acetil-Hexosaminidases/análiseRESUMO
Neutral alpha-glucosidase was isolated from rat liver by Sephadex G-150 gel filtration and polyacrylamide gel electrophoresis at pH 8.9. The enzyme was found to exist in two major forms: alpha-glucosidase AB and alpha-glucosidase C. The neutral alpha-glucosidase C was purified to apparent homogeneity and biochemically characterized. The enzyme form accounts for 25-30% of the total enzyme activity, has a pH optimum at 6.0-6.5 and is thermostable. The apparent Km values for alpha-glucosidase C with maltose, MUF-alpha-D-glucopyranoside and glycogen as substrates were 1.22 mM, 0.47 mM and 68.9 mg, respectively. The finding that glycogen can serve as substrate for neutral alpha-glucosidase C suggests its involvement in glycogen metabolism.
Assuntos
Fígado/enzimologia , alfa-Glucosidases/isolamento & purificação , alfa-Glucosidases/metabolismo , Animais , Cromatografia em Gel , Eletroforese em Gel de Poliacrilamida , Estabilidade Enzimática , Glicogênio/metabolismo , Temperatura Alta , Concentração de Íons de Hidrogênio , Immunoblotting , Cinética , Ratos , Especificidade por Substrato , Termodinâmica , alfa-Glucosidases/químicaRESUMO
Serotonin and tyramine affected dissimilarly the enzyme activity involved in degradation of glycogen in isolated rat hepatocytes. Serotonin inhibited hydrolytic enzymes acid alpha-glucosidase, alpha-amylase and amylo-1,6-glucosidase but activated phosphorylase inducing a decrease of glycogen content in cells. Tyramine inhibited acid alpha-glucosidase and amylo-1,6-glucosidase, did not affect the alpha-amylase and phosphorylase activities and increased content of glycogen in cells. Tyramine may be used as stimulator of glycogen accumulation in liver cells.