A B S T R A C T The enzyme activities involved in fructose metabolism were measured in samples of human liver. On the basis of U/g of wet-weight the following results were found: ketohexokinase, glycerol kinase, 0.62. Sorbitol dehydrogenases (25.0 U/g), hexosediphosphatase (4.06 U/g), hexokinase (0.23 U/g), and glucokinase (0.08 U/g) were also measured. Comparing these results with those of the rat liver it becomes clear that the activities of alcohol dehydrogenases (NAD and NADP) in rat liver are higher than those in human liver, and that the values of ketohexokinase, sorbitol dehydrogenases, and hexosediphosphatase in human liver are lower than those values found in rat liver. Human liver contains only traces of glycerate kinase.The rate of fructose uptake from the blood, as described by other investigators, can be based on the activity of ketohexokinase reported in the present paper. In human liver, ketohexokinase is present in a four-fold activity of glucokinase and Requests for reprints should be addressed to Dr.
No abstract
No abstract
(Adenine-'4C) or (y3'P)-labelled 2,2'[1-(9-adenyl)-I '-(tri-, diphosphoryl-oxymethy1)l-dihydroxydiethylether (rroANP) was obtained from ANP by cleavage of the C-2'-C-3' bond by sodium periodate oxidation and subsequent borohydride reduction.Binding of rroANP to rat liver mitochondria revealed carrier-linked (atractyloside-sensitive) and unspecific (atractyloside-insensitive) binding but no transfer across the inner mitochondrial membrane. Kinetic data indicate rroANP as acompetitive inhibitor for AhT uptake with Ki = 9.3 x M. Experimental rroANP confirmed that an intact adenine base and three anionic charges of the phosphate chain are essential for the recognition between AM'-carrier and nucleotide but insufficient for the induction of a transmembrane ANP exchange. In addition mobilisation of the carrier-nucleotide complex requires an intact ribofuranoside ring system. Mitochondria1 AM' translocation is a key step for energy supply processes of aerobic organisms. Much interest has been directed to the catalytic mechanism of this carrier-mediated adenine nucleotide transfer across the inner mitochondrial membrane in the last decade [1,2]. Up to now, the molecular nature of the membrane integral Am-carrier is still unknown, but lately isolation and characterisation techniques have been developed [3 -61. Studies of specific interactions between the carrier and its substrate are actually still confined to measurements in situ. Analogues of the adenine nucleotides, therefore, are very useful probes for studying structural and electronic factors involved in the catalytic mechanism of AAPdependent biological processes in general and, as shown in this paper, on mitochondrial ANP translocation [7,8, and cited references].This publication describes carrier-linked binding and exchange properties of the ribose-ring opened Am-analogue 2,2'[1-(9-adenyl)-l'-(tri-, diphosphoryl-oxymethyl)]-dihydroxydiethylether rro-AT(D)P. Our interest was directed to investigations of struc- tural requirements of the mitochondrial membrane integral Am-carrier for substrate binding and transfer across the inner mitochondrial membrane. EXPERIMENTAL PROCEDURE MATERIALS Preparation of rroATPThe ribose-ring opened ATP analogue was prepared by cleavage of the C-2' -C-3' bond in a modidure [9 -111 by sodium periodate oxidation and subsequent sodium borohydride reduction.8.25 pmol ATP disodium salt was dissolved in 0.22 ml 0.1 M phosphate buffer pH 7.0 and 0.44 ml 0.1 M sodium periodate were added. Excess periodate was destroyed by addition of 0.045 ml 1 M glucose solution. (Reaction time 45 min). After oxidation 5 m g sodium borohydride solved in 0.43ml double distilled water was added. The pH of the reaction mixture was adjusted to 7.8 by 2 M sodium acetate buffer pH 5.2. After a reaction period of 24 h at room temperature excess sodium borohydride was destroyed by adjusting the pH to 5.2. The reaction mixture was then applied to a DEAE-cellulose column (Whatman DEAE 32-cellulose, 1 x 5 cm). The modified ANP was eluted by a linear gradient of trieth...
I. Various thiophosphate analogues of adenine nucleotides, such as adenosine 5'-0-( l-thiotriphosphate), adenosine 5'-0-(3-thiotriphosphate), adenosine 5'-0-( I-thiodiphosphate) and adenosine 5'-0-(2-thiodiphosphate) as well as the 1-N-oxides of adenosine 5'-0-tri(and-di)-phosphates show atractyloside-sensitive (i.e. adenine nucleotide-"carrier"-linked) and insensitive (non-"carries"-linked) binding properties to rat liver mitochondria. -Em. J. Biochem. 40 (1973)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.