scholarly journals Characterization of vitamin K-dependent carboxylase from the livers from the adult ox and dicoumarol-treated calf.

1982 ◽  
Vol 201 (2) ◽  
pp. 249-258 ◽  
Author(s):  
L Uotila ◽  
J W Suttie
Keyword(s):  
Rat Liver ◽  
Vitamin K ◽  
Pyridoxal Phosphate ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Ph Optimum ◽  
Carboxylase Activity ◽  
Triton X ◽  
Assay Conditions

The properties of the microsomal vitamin K-dependent carboxylase from the livers of the adult ox and dicoumarol-treated calf were investigated. The enzymes from both sources utilized glutamic residues of synthetic peptides as substrates and could be solubilized with Triton X-100 similarly to the enzyme from vitamin K-deficient rat liver. Under the optimal assay conditions, the microsomes from calf liver had peptide carboxylase activity comparable with that of the rat liver microsomes and 6.5-fold that of adult ox liver microsomes. The apparent Km for reduced vitamin K and the ionic strength optima of the calf and adult ox enzyme clearly differ from those of the rat enzyme. Pyridoxal phosphate activated the adult ox carboxylase only slightly, whereas the calf enzyme was activated by pyridoxal phosphate as effectively as was the enzyme from the vitamin K-deficient rat. Mn2+ activated the adult ox enzyme 9-fold and calf enzyme 22-fold under optimal conditions (no KCl). Three other divalent metal cations (Ca2+, Ba2+, and Mg2+) activated the adult ox and calf enzymes to about half the extent caused by Mn2+, KCl inhibited this activation. The vitamin K-dependent carboxylase from the dicoumarol-treated calf is apparently more tightly bound to the microsomal membrane than is the adult ox enzyme. In many other respects (pH optimum), temperature optimum, Km values for peptide substrate, substrate specificity, inhibitor effects), the properties of the adult ox and calf enzymes resemble closely those of the rat enzyme.

scholarly journals Characterization of the interaction between p100, a novel G-protein-related protein, and rat liver endosomes

1991 ◽  
Vol 280 (1) ◽  
pp. 171-178 ◽  
Author(s):  
L M Traub ◽  
E Shai ◽  
R Sagi-Eisenberg
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Trypsin Treatment ◽  
Putative Receptor ◽  
Microsomal Membranes ◽  
Direct Binding ◽  
Triton X ◽  
Binding Sequence

p100 is a recently identified 100 kDa protein which shares a putative receptor-binding sequence with the signal transducing G-proteins Gt and Gi. In liver, p100 immunoreactivity is distributed between the cytosolic and the microsomal fractions [Traub, Evans & Sagi-Eisenberg (1990) Biochem. J. 272, 453-458; Udrisar & Rodbell (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 6321-6325]. More specifically, we have localized the membrane-associated form of p100 to an endosomal subfraction of rat liver microsomes. In this study we have investigated the nature of the interaction between p100 and microsomal membranes. p100 was located on the cytoplasmic surface of the microsomal vesicles, and could be released by treatment with 0.5 M-NaCl or 0.5 M-Tris/HCl, pH 7.0. However, p100 was not released by non-ionic detergents, such as Triton X-100. Binding of p100 to the membrane was reversible, as both membrane-released and cytosolic p100 could re-bind stripped (Tris-washed) microsomes. Soluble p100 could not, however, bind to untreated microsomes. Binding to stripped microsomes approached saturation and was inhibited by up to 60% by either heat treatment or mild trypsin treatment of the vesicles. This implies that the interaction between p100 and the microsomal vesicles involves the direct binding of p100 to vesicular proteins. This binding was regulated by both adenine and guanine nucleotides. As p100 contains a region similar to the C-terminal decapeptide of alpha i, (the alpha-subunit of Gi) and has a localization that is restricted to an endosomal subfraction, we propose that cytosolic p100 may bind to cytoplasmically exposed domains of internalized receptors. Thus, like the adaptins, p100 may be involved in the process of sorting and receptor trafficking through the endosomal compartment of the cells.

Dolichol and polyprenol kinase activities in microsomes from etiolated rye seedlings

1992 ◽  
Vol 70 (6) ◽  
pp. 455-459 ◽  
Author(s):  
Robert T. Rymerson ◽  
Kenneth K. Carroll ◽  
Jack W. Rip
Keyword(s):  
Rat Liver ◽  
Divalent Cations ◽  
Liver Microsomes ◽  
Microsomal Protein ◽  
Rat Liver Microsomes ◽  
Ph Optimum ◽  
Dolichyl Phosphate ◽  
Triton X ◽  
Enhance Activity ◽  
Better Than

Dolichol kinase activity in microsomes from etiolated rye seedlings had a pH optimum at 8 with a shoulder at pH 6.5. Triton X-100 (0.4%) was required for optimum activity. Exogenous divalent cations did not enhance activity, although Mg+2 was added routinely. Rye microsomes were found to contain dolichol and polyprenol in a ratio of 3 to 2. Rye, soybean embryo, and rat liver microsomes catalyzed the synthesis of 78, 52, and 516 nmol [14C]dolichyl phosphate/(mg microsomal protein∙h) compared with 21, 22, and 49 nmol [3H]polyprenyl phosphate/(mg microsomal protein∙h), respectively. It is clear that microsomes from plant systems can catalyze the phosphorylation of polyprenol better than rat liver when compared with their abilities to catalyze the phosphorylation of dolichol. It is not known whether one or more kinases is responsible for catalyzing the phosphorylation of these two closely related groups of compounds.Key words: dolichol, polyprenol, dolichyl phosphate, polyprenyl phosphate, kinases.

scholarly journals In Vitro Characterization of Borneol Metabolites by GC--MS Upon Incubation with Rat Liver Microsomes

2008 ◽  
Vol 46 (5) ◽  
pp. 419-423 ◽  
Author(s):  
R. Zhang ◽  
C.-h. Liu ◽  
T.-l. Huang ◽  
N.-s. Wang ◽  
S.-q. Mi
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
In Vitro Characterization

scholarly journals Characterization of solubilized insulin receptors from rat liver microsomes. Existence of two receptor species with different binding properties

1986 ◽  
Vol 154 (2) ◽  
pp. 281-287 ◽  
Author(s):  
Rudiger KOCH ◽  
Arno DEGER ◽  
Hans-Martin JACK ◽  
Karl-Norbert KLOTZ ◽  
Dieter SCHENZLE ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Insulin Receptors ◽  
Rat Liver Microsomes ◽  
Binding Properties

Separation and Characterization of Carboxyl-linked Glucuronides of Bile Acids in Incubation Mixture of Rat Liver Microsomes

Steroids ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 186-192 ◽  
Author(s):  
Junichi Goto ◽  
Naoaki Murao ◽  
Chifumi Nakada ◽  
Takashi Motoyama ◽  
Junji Oohashi ◽  
...  
Keyword(s):  
Bile Acids ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Incubation Mixture ◽  
Rat Liver Microsomes
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