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M Zydowo

Publications and source records attributed to M Zydowo.

At least 19 recordsLinked to original sources
PubMed1985

Modification of the catalytic and regulatory properties of beef heart AMP-deaminase by DTNB treatment.

In beef heart AMP-deaminase (EC 3.5.4.6.), 7 SH-groups out of 26 half-cysteine residues in the protein molecule have been shown to be accessible to alkylation by DTNB in the absence of ATP. The addition of ATP showed that only 6 SH-groups were accessible. DTNB-modified enzyme showed about 30% of the native catalytic activity but no sensitivity to the ATP-activating effect. Almost full reactivation of the modified enzyme and the restoration of the activatory effect of ATP could be achieved by exhaustive dialysis against mercaptoethanol.

AMP Deaminase↗
PubMed1985

Regulation of trout gill AMP deaminase by lipid bilayers. Effects of phospholipid composition and temperature.

Trout gill AMP deaminase is inhibited by liposomes made of synthetic phosphatidylcholines containing higher saturated fatty acids. A preincubation of 1 hr, at 4 degrees C, was necessary to obtain the maximal effect. At 4 or 25 degrees C, these phospholipids modified essentially the substrate affinity of the enzyme by increasing the Michaelis constant proportionally to the length of the fatty acid chain. At 13 degrees C, the liposomes decreased the Hill coefficient also, thus inducing a negative cooperativity. Natural phosphatidylcholine and phosphatidylserine were without significant effect on gill AMP deaminase while natural sphingomyelin exhibited a similar effect to that shown in the presence of synthetic phosphatidylcholines. These results are discussed in relation to a possible effect of sphingomyelins in vivo.

AMP Deaminase↗
PubMed1985

Metabolic characterization of three hamster melanoma variants.

Some enzyme activities and metabolic features of the black Ma melanotic, brown MI melanotic and Ab amelanotic melanomas of hamster were investigated. The activities of hexokinase and phosphofructokinase were similar in all three melanomas, the activity of NAD-dependent glycerol-3-phosphate dehydrogenase was higher in the amelanotic melanoma and that of pyruvate kinase and lactate dehydrogenase were slightly lower in MI than in the other tumors. The activities of citrate synthase, succinate dehydrogenase and malate dehydrogenase were higher in the Ma and MI melanotic melanomas than in the Ab amelanotic melanoma. The rate of labeled CO2 production from 6-14C-glucose, 1,5-14C-citric acid and U-14C-glutamine was about 2 times higher in melanotic melanomas than in amelanotic one, while no significant differences among the three melanomas were found in respect to 1-14C-glucose and U-14C-glycerol-3-phosphate. The production of 14CO2 was much higher from 1-14C-glucose than from 6-14C-glucose in all the melanomas studied. L-DOPA stimulated the production of 14CO2 from 1-14C-glucose much stronger in the Ma and MI melanomas than in the Ab melanoma. In none of the tumors the incorporation from 6-14C-glucose to CO2 was affected by L-DOPA. It is postulated that oxidation of glucose via the pentose phosphate cycle is involved in melanogenesis.

Animals↗
PubMed1983

The effect of phospholipid bilayers on AMP-deaminase from rat tissues.

The ATP-activated adenylate deaminase (EC 3.5.4.6) from the rat heart, kidney, spleen, liver and brain showed a mixed-type allosteric activation under the influence of phosphatidylcholine-containing liposomes, but no effect was observed on the non-activated enzyme isolated from all these tissues but the brain. The brain enzyme was activated by the liposomes also in the absence of ATP. No effect of the phosphatidylcholine-containing liposomes could be shown on the adenylate deaminase isolated from skeletal muscle and red blood cells. The phosphatidate-containing liposomes exerted an inhibitory effect on the enzyme isolated from the heart, kidney and brain, being without effect on the enzyme from skeletal muscle.

AMP Deaminase↗
PubMed1980

AMP deaminase from the rat heart injured by high doses of vitamin D.

Adenylate deaminase (EC 3.5.4.6) has been isolated from the hearts of healthy rats and from the rats with cardionecrosis induced by administration of vitamin D in high doses. Crude extract from the necrotic hearts catalysed adenylate deamination with a higher maximum velocity and a higher apparent Km value than the extract from healthy hearts. The enzyme from healthy animals was activated by ATP (Km-type of activation); the maximum velocity of the ATP-activated enzyme could be increased in about 50% by preincubation with phosphatidylcholine-containing liposomes. Liposomes had no effect on the enzyme isolated from the hearts of vitamin D-intoxicated animals, whereas other kinetic and regulatory properties were similar to those of the enzyme from healthy hearts. Kinetic and regulatory parameters of adenylate deamination in the hearts of rats which survived cardionecrosis returned to normal values 6 weeks after vitamin D intoxication.

AMP Deaminase↗
PubMed1980

Purification and regulatory properties of pig kidney AMP deaminase.

AMP deaminase (EC 3.5.4.6) from pig kidney was purified about 1200-fold by chromatography on cellulose phosphate. The enzyme showed a sigmoid-shaped substrate saturation curve which was converted to hyperbolic by addition of ATP. The ATP-activated enzyme was sensitive to phosphatidylcholine-containing liposomes which caused a further increase of activity by lowering the S0.5 value and increasing V max. In the absence of ATP, the enzyme was not sensitive to phosphatidylcholine-containing liposomes. Phosphatidate-containing liposomes exerted an inhibitory effect both in the presence and absence of ATP. In the presence of ATP phosphatidate was a non-competitive inhibitor. Orthophosphate was found to be a competitive inhibitor of AMP deaminase from pig kidney. When the phosphatidylcholine/phosphatidic acid ratio in liposomes was 2.7, AMP deaminase was activated, whereas when this ratio dropped below 2.1, liposomes exerted a non-competitive inhibitory effect.

AMP Deaminase↗
PubMed1979

Reconstruction of rat skeletal muscle glycerophosphate shuttle.

The activity of alpha-glycerophosphate shuttle in homogenate and in a reconstructed system (isolated mitochondria and cytoplasm) from rat skeletal muscle is presented. The influence of some inhibitors of mitochondrial alpha-glycerosphate dehydrogenase on the activity alpha-glycerophosphate shuttle is demonstrated. The possible operativity of alpha-glycerophosphate shuttle in skeletal muscle in vivo is discussed.

Animals↗
PubMed1979

Comparative studies on muscle AMP-deaminase--I. Purification, molecular weight, subunit structure and metal content of the enzymes from rat, rabbit, hen, frog and pikeperch.

1. AMP-deaminase (EC 3.5.4.6) from skeletal muscle of frog and pikeperch was purified to homogeneity and compared with the homogeneous enzymes purified from rat, rabbit and hen skeletal muscle. 2. Their molecular weight was close to 280,000, every enzyme consisted of four identical subunits of molecular weight about 70,000. 3. All enzymes were found to contain about two atoms of zinc per molecule. 4. Minor differences of u.v.-absorption spectra between amphibian and fish muscle enzyme as compared with mammalian and bird muscle enzyme were found.

AMP Deaminase↗