Serum catalase enzyme activity in liver diseases

Serum catalase activity was moderately increased in fatty liver, acute alcoholic hepatitis and in the decompensated form of cardiac circulatory failure. It showed significant increase in acute yellow atrophy and in toxic hepatitis while no changes were detected in liver cirrhosis and viral hepatitis. Serum catalase activity showed a good correlation (r = 0.820) with the serum glutamate dehydrogenase activity. In accordance with our results, the inexpensive assay of serum catalase activity is suggested for the detection of severe liver cell damage.     

Possible involvement of histidine residues in the loss of enzymatic activity of rat liver malic enzyme during aging

During aging there is a decrease in activity of the malic enzyme in rat liver. The "old" malic enzyme is about 36% less active than the "young" enzyme. Some properties and modifications of amino acid residues are studied here (--SH, arginine, methionine, histidine, lysine) to try and check on the existence of any relationship between them and the loss of enzymatic activity during aging. Diethyl pyrocarbonate measurements indicate that the old enzyme has 1 histidine residue less than the young enzyme. Moreover, the treatment of the young enzyme with ascorbate for 15 min produces the loss of 36% of the enzymatic activity and the loss of 1.2 histidine residues. These results suggest that during aging the modification of the histidine residue could be involved in the loss of its enzymatic activity.     

Differential loss of enzyme activity by vitC and iron containing proteins

Our earlier studies showed that rabbit muscle phosphoglucomutase was irreversibly inactivated by exposure to a mixture of vitamin C, FeCl3 and O2. The enzyme lost about 70% of its phosphate (V.V. Desphande and J.G. Joshi, J. Biol. Chem. 260, 754-764, 1985). The present report shows that several other iron proteins can substitute for FeCl3 to a varying degree. The rate of inactivation by FeCl3 greater than ferritin greater than hemoglobin = hemerythrin greater than transferrin = ferridoxin = vitamin C. These iron compounds also produced dephosphoenzyme but did not dephosphorylate ATP, ADP, AMP or phospholipids.     

Fluorimetric coupled enzyme assay for lysoplasmalogenase activity in liver.

Two new proteins with apparent molecular masses of 53 kDa and 190 kDa have been identified in both sarcoplasmic reticulum and human blood platelets using a monoclonal antibody, FII1b5. The sarcoplasmic reticulum FII1b5 antigens were present in the terminal cisternae fraction, but were absent from light sarcoplasmic reticulum. The platelet and skeletal muscle proteins were not sensitive to digestion with endoglycosidase H under conditions that removed carbohydrate from the 53 kDa glycoprotein in sarcoplasmic reticulum or GPIIIa in platelet microsomes and did not bind 45Ca in a nitrocellulose overlay calcium-binding assay. These results distinguished the FII1b5 antigens from the 53 kDa glycoprotein and calsequestrin of sarcoplasmic reticulum. The 190 kDa platelet and sarcoplasmic reticulum proteins were extracted from membranes with high concentrations of NaCl, indicating that the high molecular mass FII1b5 antigens are peripherally associated with the bilayers. In contrast, the platelet and muscle 53 kDa proteins remained membrane-bound in the presence of high salt concentrations, suggesting that they are integral proteins.     

Angiotensin-converting enzyme activity in experimental alcoholic fatty liver of the rat

Angiotensin-converting enzyme (ACE) activity was found increased in serum of patients with chronic alcoholism. We studied this enzymatic activity in serum and liver tissue of rats with alcoholic fatty liver due to prolonged intake of ethanol with a liquid diet, according to De Carli and Lieber. Serum and liver ACE activity did not show any significant increase in rats with alcoholic fatty liver when compared with controls, whereas gamma-glutamyltransferase activity exhibited a striking enhancement in serum and liver. Our data suggest that ACE is not an alcohol-induced enzyme in the experimental rat model.     

High malic enzyme activity in tumor cells and its cross-reaction with antipigeon liver malic enzyme serum

Summary Rabbit antibodies against pigeon liver malic enzyme (EC 1.1.1.40) were prepared. The antiserum gave single precipitation line with crude pigeon liver extract. Cross reaction was observed with partially purified malic enzyme or crude extract from chicken liver. Positive cross reaction was also observed with the concentrated cytosolic fraction of two human carcinoma cell lines which were demonstrated to contain high malic enzyme activity. All other proteins examined did not react with the antibodies. When purified pigeon liver malic enzyme was mixed with the antiserumin vitro, a time-dependent inactivation of the enzyme activity was observed. Protection of the enzyme activity against antiserum inactivation was afforded by NADP⁺ orL-malate. Metal Mn²⁺ gave little protection.     

Findings of trigonelline demethylating enzyme activity in various organisms and some properties of the enzyme from hog liver

Trigonelline demethylating enzyme activity was found widely in animals, plants and microorganisms. Very high enzyme activity of this enzyme was detected in hog liver. Properties of the hog liver enzyme were investigated. Optimum pH for the enzymic reaction was observed at 8.5. The Km value for trigonelline was calculated at 2.77 mM. Addition of any cofactor is not required for the reaction The enzyme activity was inhibited by heavy metal ions. The reaction product was identified as nicotinic acid. Proposed enzyme reaction mechanism and the role of this enzyme in biosynthesis and metabolism of NAD are discussed.     

Activation of 4-alpha-glucanotransferase activity of porcine liver glycogen debranching enzyme with cyclodextrins

Glycogen debranching enzyme (GDE) is a single polypeptide chain containing distinct active sites for 4-alpha-glucanotransferase and amylo-alpha-1,6-glucosidase activities. Debranching of phosphorylase limit dextrin from glycogen is carried out by cooperation of the two activities. We examined the effects of cyclodextrins (CDs) on debranching activity of porcine liver GDE using a fluorogenic branched dextrin, Glcalpha1-4Glcalpha1-4Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B5/84), as a substrate. B5/84 was hydrolyzed by the hydrolytic action of 4-alpha-glucanotransferase to B5/81 and maltotriose. The fluorogenic product was further hydrolyzed by the amylo-alpha-1,6-glucosidase activity to the debranched product, Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (G8PA), and glucose. alpha-, beta- and gamma-CDs accelerated the liberation of B5/81 from B5/84, indicating that the 4-alpha-glucanotransferase activity was activated by CDs to remove the maltotriosyl residue from the maltotetraosyl branch. This led to acceleration of B5/84 debranching. The extent of 4-alpha-glucanotransferase activation increased with CD concentration before reaching a constant value. This suggests that there is an activator binding site and that the binding of CDs stimulates 4-alpha-glucanotransferase activity. In the porcine liver, glycogen degradation may be partially stimulated by the binding of a glycogen branch to this activator binding site.     

Temperature and enzyme activity in poikilotherms. Isocitrate dehydrogenases in rainbow-trout liver

1. The kinetics of the thermally induced enzyme variants of the supernatant NADP-isocitrate dehydrogenase from rainbow-trout liver are investigated. 2. Fish acclimatized to 2 degrees C (cold-adapted enzyme) and 17 degrees C (warm-adapted enzyme) show different relative distributions of the three NADP-isocitrate dehydrogenase isoenzymes; this has been demonstrated with electrophoresis and electrofocusing techniques. 3. Plots of K(m) versus temperature for the cold-adapted and warm-adapted enzyme variants are complex in nature with apparent maximal enzyme-substrate affinity corresponding to the temperature at which the trout is acclimatized. Both substrates, dl-isocitrate and NADP(+), give similar curves although the magnitude of the K(m) change with temperature is much decreased in the case of NADP(+). 4. E(a) values of approx. 18kcal/mol were determined for both the cold-adapted and warm-adapted enzyme variants. 5. In an attempt to determine how velocities can be increased at low temperatures, cation, pH requirements, metabolite and enzyme concentrations were examined. 6. NAD-isocitrate dehydrogenase could not be detected in trout tissues.     

Imidazolinone-induced loss of acetohydroxyacid synthase activity in maize is not due to the enzyme degradation

Acetohydroxyacid synthase (AHAS), the first enzyme leading to the biosynthesis of valine, leucine, and isoleucine, is inhibited by different chemical classes of herbicides. There is a loss in the extractable AHAS activity in imidazolinone-treated plants. Immunological studies using a monoclonal antibody against AHAS revealed no degradation of AHAS protein in imidazolinone-treated maize (Zea mays) plants. Therefore, the loss in AHAS activity is not due to the loss of AHAS protein.