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Spór o źródła mocy katalitycznej enzymów

100%

Hutny J.

Postępy Biochemii

2010

tom 56

nr 4

Kinetics of hog pancreas alpha-amylase; Theoretical model of the dual-site enzyme

100%

Hutny J.

tom 28

nr 2

Modele i amylolizy i topografia miejsc wiążących amylaz

100%

Hutny J.

tom 25

nr 4

Further studies on the role of phospholipids in determining the characteristics of mitochondrial binding sites for type I hexokinase

63%

Hutny J. , Wilson J. E.

nr 4

Previous work has indicated that two types (A and B) of binding sites for hexokinase exist, but in different proportions, on brain mitochondria from various species. Hexokinase is readily solubilized from Type A sites by glucose 6-phosphate (Glc-6-P), while hexokinase bound to Type B sites remains bound even in the presence of Glc-6-P. Type A:Type B ratios are approximately 90:10, 60:40, 40:60, and 20:80 for brain mitochondria from rat, rabbit, bovine and human brain, respectively. The present study has indicated that MgCl2-dependent partitioning of mitochondrially bound hexokinase into a hydrophobic (Triton X-114) phase is generally correlated with the proportion of Type B sites. This partitioning behavior is sensitive to phospholipase C, implying that the factor(s) responsible for conferring hydrophobic character is(are) phospholipid(s). Substantial differences were also seen in the resistance of hexokinase, bound to brain mitochondria from various species, to solubilization by Triton X-100, Triton X-114, or digitonin. This resistance increased with proportion of Type B sites. Enrichment of bovine brain mitochondria in acidic phospholipids (phosphatidylserine or phosphatidylinositol), but not phosphatidylcholine or phosphatidylethanolamine, substantially increased solubilization of the enzyme after incubation at 37°C. Collectively, the results imply that the Type A and Type B sites are located in membrane domains of different lipid composition, the Type A sites being in domains enriched in acidic phospholipids which lead to greater susceptibility to solubilisation by Glc-6-P.

Activity of glycogen depolymerizing enzymes in extracts from brain tumor tissue [anaplastic astrocytoma and glioblastoma multiforme]

44%

Kotonski B. , Wilczek J. , Madej J. , Zarzycki A. , Hutny J.

Acta Biochimica Polonica

2001

tom 48

nr 4

An approximately threefold increase in glycogenolytic activity of the neutral a-1,4-glucosidase and a twofold increase in the same activity of the acid isoform have been found in extracts of anaplastic astrocytoma and glioblastoma multiforme tumors of brain tissue. "Maltase activity" of the respective enzymes increased by 60-80% in both kinds of tumor extracts. However a significant decrease in a-amylase and almost complete disappearance of phosphorylase activities have also been found in both kinds of tumors.