Liver catalytic properties

Kedishvili NY, Bosron WF, Stone CL, Hurley TD, Peggs CF, Thomasson HR, Popov KM, Carr LG, Edenberg HJ, Li T-K. Cloning and expression of a human stomach alcohol dehydrogenase Comparison of structure and catalytic properties with the liver isoenzymes. J Biol Chem 1995 280 3625-3630. 

E. The catalytic properties of the liver enzyme are significantly different than those of the RBC enzyme. 

Correct answer = B. Cellular damage is directly related to decreased ability of the cell to regenerate reduced glutathione, for which large amounts of NADPH are needed. RBCs have plenty of glutathione peroxidase. Catalytic properties of glucose 6-phosphate dehydrogenase in liver and RBCs are very similar. 

Rotchell, J.M., G.B. Steventon and D.J. Bird. Catalytic properties of CYP1A isoforms in the liver of an agnathan Lampetrafluviatilis) and two species of teleost Pleuronectes flesus. Anguilla anguilla). Comp. Biochem. Physiol. 125C 203—214, 2000. 

Pll. Pontremoli, S., Luppis, B., Wood, W. A., Traniello, S., and Horecker, B. L., Fructose diphosphatase from rabbit liver. II. Changes in catalytic properties Induced by dinitrofluorobenzene. J. Biol. Chem. 240, 3464-3468 (1965). 

Freeman, C., and Hopwood, J. J., Human liver sulfamate sulfohydrolase—Determinations of native protein and subunit molecular weight values and influence of substrate aglycone structure on catalytic properties. Biochem. J. 234, 83-92 (1986). 

W2. Warholm, M., Guthenberg, C., and Mannervik, B., Molecular and catalytic properties of glutathione transferase mu from human liver. An enzyme efficiently conjugating epoxides. Biochemistry 22, 3610-3617 (1983). 

Abita, J.P., Parniak, M., and Kaufman, S., The activation of rat liver phenylalanine hydroxylase by limited proteolysis, lysolecithin, and tocopherol phosphate. Changes in conformation and catalytic properties, J. Biol. Chem. 259 (23), 14560-14566,1984. 

The D-galactosylceramide jS-D-galactosidase from the liver of a case of Krabbe s disease has been purified. The physical properties of this enzyme were very similar to those of a control from normal liver tissue but the catalytic properties and stability of the enzyme protein were severely affected in the mutant. The findings indicated that the mutation in Krabbe s disease leads to the synthesis of normal quantities of a catalytically and structurally altered protein. 

The enzyme Candida utilis 6-phosphogluconate dehydrogenase with carbon-13 enriched to 90 atom% has been obtained by growing the yeast with Relabelled acetic acid as the sole carbon source [186]. Carbon-13 composition had very little, if any, effect on the catalytic properties of the enzyme. Sodium [ RC]lactate has been used to study the conversion of lactate to liver glycogen in the rat. Lactate labelled with C at position 2 and C at position 3 was also used. Carbon-13 was measured by mass spectrometry [187]. Similar experiments were carried out with RC-labelled propionate and C- and C-labelled propionate [188]. 

The most striking observation with respect to lactic dehydrogenase is the multiplicity of enzyme molecules with similar catalytic properties. A number of molecules having lactic dehydrogenase activity separate upon electrophoresis. This observation was made with preparations obtained from different tissues. Thus, by electrophoresis on agar, polyacrylamide, or other suitable media, five lactic dehydrogenases have been separated from tissues such as heart and kidney, and three from liver and plasma. 

A coenzyme role of biotin in the reaction catalyzed by oxaloacetate carboxylase has been proposed on the basis of studies made with the purified enzyme, which suggest a close association between the enzyme s biotin content and the catalytic properties of the protein. The purified enzyme preparation contains 3 mpg of biotin per mg of protein. Biotin as a CO2 carrier in the CO2 fixation reaction was further supported in studies made on enzyme preparations obtained from birds and mammalian livers. These preparations catalyze the reversible conversion of pyruvate into oxaloacetate in the presence of ATP. 

Protein synthesis and membrane formation in embryonic and postnatal rat liver occurs faster than in the liver of adult individuals. It was demonstrated that an increase in transferase activity coincided with an increase in hydrolase activity. However, the ratio between these two activities was not constant. This ratio increased from 0.8 (day of delivery) to 2.6 (4-7 days after delivery) and subsequently decreased to 1-2 (adult rat). These fluctuations were caused by the binding of enzyme molecules with microsomal membranes, and differences in the expression of catalytic properties were caused by the relative proportions of membrane-bound and free fractions. It was demonstrated with the aid of enzyme extractions with the nonionic detergent Triton X-100 and sodium deoxycholate (Duck-Chong and Poliak, 1973 Fig. 38). There are bacterial mutants with reduced esterase activity. In some of them esterase activity is reduced because of low levels of enzyme synthesis. Other mutants have low esterase activity due to the weakening of the association of the membrane-enzyme compound (Frehel et al., 1974). 

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