scholarly journals Effects of riboflavin deficiency and clofibrate treatment on the five acyl-CoA dehydrogenases in rat liver mitochondria

1988 ◽  
Vol 254 (2) ◽  
pp. 477-481 ◽  
Author(s):  
K Veitch ◽  
J P Draye ◽  
F Van Hoof ◽  
H S A Sherratt
Keyword(s):  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Straight Chain ◽  
Riboflavin Deficiency ◽  
Deficient Diet ◽  
Mitochondrial Fractions ◽  
Chain Acyl ◽  
Branched Chain ◽  
Acyl Coa Dehydrogenases ◽  
Riboflavin Deficient

Rats were maintained on a riboflavin-deficient diet or on a diet containing clofibrate (0.5%, w/w). The activities of the mitochondrial FAD-dependent straight-chain acyl-CoA dehydrogenases (butyryl-CoA, octanoyl-CoA and palmitoyl-CoA) and the branched-chain acyl-CoA dehydrogenases (isovaleryl-CoA and isobutyryl-CoA) involved in the degradation of branched-chain acyl-CoA esters derived from branched-chain amino acids were assayed in liver mitochondrial extracts prepared in the absence and presence of exogenous FAD. These activities were low in livers from riboflavin-deficient rats (11, 28, 16, 6 and less than 2% of controls respectively) when prepared in the absence of exogenous FAD, and were not restored to control values when prepared in 25 microM-FAD (29, 47, 28, 7 and 17%). Clofibrate feeding increased the activities of butyryl-CoA, octanoyl-CoA and palmitoyl-CoA dehydrogenases (by 48, 116 and 98% of controls respectively), but not, by contrast, the activities of isovaleryl-CoA and isobutyryl-CoA dehydrogenases (62 and 102% of controls respectively). The mitochondrial fractions from riboflavin-deficient and from clofibrate-fed rats oxidized palmitoylcarnitine in State 3 at rates of 32 and 163% respectively of those from control rats.

scholarly journals A study of the metabolism of [U-14C]3-methyl-2-oxopentanoate by rat liver mitochondria using h.p.l.c. with continuous on-line monitoring of radioactive intact acyl-coenzyme A intermediates

1986 ◽  
Vol 235 (2) ◽  
pp. 343-350 ◽  
Author(s):  
A G Causey ◽  
B Middleton ◽  
K Bartlett
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Intermediary Metabolism ◽  
Rat Liver Mitochondria ◽  
Powerful Method ◽  
Reverse Phase ◽  
Mitochondrial Fractions ◽  
On Line ◽  
Riboflavin Deficient ◽  
Acyl Coenzyme A

A reverse-phase h.p.l.c. system for the resolution of the acyl-CoA intermediates of the degradation of 3-methyl-2-oxopentanoate is described. The validation of a method for the measurement of radioactive intermediates produced by the incubation of [U-14C]3-methyl-2-oxopentanoate with rat liver mitochondrial fractions is described. The absence of bicarbonate caused the accumulation of [14C]propionyl-CoA. The accumulation of [14C]2-methylbutyryl-CoA was observed in incubations with mitochondrial fractions derived from riboflavin-deficient animals. Studies of the accumulation of labelled intermediates with time suggest that there is regulation of the pathway of isoleucine degradation at methylmalonyl-CoA mutase, as suggested for valine [Corkey, Martin-Requero, Walajtys-Rode, Williams & Williamson (1982) J. Biol. Chem. 257, 9668-9676]. These studies demonstrate that h.p.l.c. with on-line continuous radiochemical detection is a powerful method for the investigation of the control of intermediary metabolism.

scholarly journals The purification and properties of ox liver short-chain acyl-CoA dehydrogenase

1984 ◽  
Vol 218 (2) ◽  
pp. 511-520 ◽  
Author(s):  
L Shaw ◽  
P C Engel
Keyword(s):  
Liver Mitochondria ◽  
Short Chain ◽  
Straight Chain ◽  
Visible Absorption ◽  
Optimal Activity ◽  
Purification And Properties ◽  
Chain Acyl ◽  
Green Form ◽  
A Subunit ◽  
Acyl Coa Dehydrogenases

The FAD-containing short-chain acyl-CoA dehydrogenase was purified from ox liver mitochondria by using (NH4)2SO4 fractionation, DEAE-Sephadex A-50 and chromatofocusing on PBE 94 resin. The enzyme is a tetramer, with a native Mr of approx. 162 000 and a subunit Mr of 41 000. Short-chain acyl-CoA dehydrogenases are usually isolated in a green form. The chromatofocusing step in the purification presented here partially resolved the enzyme into a green form and a yellow form. In the dye-mediated assay system, the enzyme exhibited optimal activity towards 50 microM-butyryl-CoA at pH 7.1. Kinetic parameters were also determined for a number of other straight-chain acyl-CoA substrates. The u.v.- and visible-absorption characteristics of the native forms of the enzyme are described, together with complexes formed by addition of butyryl-CoA, acetoacetyl-CoA and CoA persulphide.

scholarly journals Mechanism of hypoglycaemic action of methylenecyclopropylglycine

1989 ◽  
Vol 259 (3) ◽  
pp. 921-924 ◽  
Author(s):  
K Melde ◽  
H Buettner ◽  
W Boschert ◽  
H P O Wolf ◽  
S Ghisla
Keyword(s):  
Plasma Concentrations ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Toxic Metabolite ◽  
Beta Oxidation ◽  
Pyruvate Metabolism ◽  
Oral Ingestion ◽  
Chain Acyl ◽  
Branched Chain ◽  
Coa Thioesters

The effects of methylenecyclopropylglycine (MCPG), the lower homologue of hypoglycin A, on starved rats are described. Upon oral ingestion of MCPG (43 mg/kg), a 50% decrease in blood glucose compared with controls was observed after 4 h. The plasma concentrations of lactate and non-esterified fatty acids were substantially increased during this period. The activity of general acyl-CoA dehydrogenase from isolated rat liver mitochondria was not significantly changed. By contrast, the activity of 2-methyl-(branched-chain)-acyl-CoA dehydrogenase decreased by over 80%. The enzyme activity of enoyl-CoA hydratase (crotonase) from pig kidneys decreased by 80% on incubation with the hypothetically toxic metabolite of MCPG, methylenecyclopropylformyl-CoA. These results suggest that the inhibition spectrum of MCPG is quite different from that of hypoglycin A and that similar physiological effects might result from inhibition of different enzymes of beta-oxidation, e.g. hypoglycaemia and lacticacidemia. Accumulation of medium-chain acyl-CoA thioesters is probably at the origin of disturbances in pyruvate metabolism.

scholarly journals THE EFFECT OF HEAT, INHIBITORS, AND RIBOFLAVIN DEFICIENCY ON MONOAMINE OXIDASE

1965 ◽  
Vol 43 (8) ◽  
pp. 1305-1318 ◽  
Author(s):  
Moussa B. H. Youdim ◽  
T. L. Sourkes
Keyword(s):  
Monoamine Oxidase ◽  
Chelating Agents ◽  
Liver Mitochondria ◽  
Borate Buffer ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Enzyme ◽  
Riboflavin Deficiency ◽  
Different Types ◽  
The Stability ◽  
Riboflavin Deficient

The stability of monoamine oxidase of rat liver mitochondria to heating has been studied, using kynuramine as substrate in a spectrophotometric assay. After suspensions of mitochondria were heated for 50 minutes at 50°, about 30% of the enzymatic activity is lost; at 53° for the same time, 50% is lost. At 60° most of the activity is lost in the first 10 minutes. Activity as a function of pH was studied; resulting curves had a shoulder around pH 6.5 and a peak at pH 7.4 in phosphate buffer (or at 8.1 in borate buffer). The corresponding curves for heated suspensions of mitochondria (50°, 30 minutes) showed a relatively greater decrease in activity at pH 7.0 than at pH 6.5. This resulted in the disappearance of the shoulder and the appearance of a new peak at pH 6.5. Tranylcypromine and iproniazid inhibited the mitochondrial enzyme more strongly at pH 8.1 (borate buffer) than at the lower pH's, but pargyline inhibited more at pH 6.5. Chelating agents such as 8-hydroxyquinoline and thenoyltrifluoroacetone inhibited the enzyme more strongly at the lower pH's. Extracts of livers of riboflavin-deficient rats showed less activity than those from vitamin-supplemented animals. Substrates and certain inhibitors of monoamine oxidase protected the enzyme from inactivation during heating, but amines that are not substrates provided no such protection. Unsuccessful attempts were made to identify different types of monoamine oxidase activity in the mitochondria fractionated on sucrose density gradients.

Factors Controlling Ketogenesis by Rat Liver Mitochondria

1972 ◽  
Vol 50 (2) ◽  
pp. 120-127 ◽  
Author(s):  
Leo P. K. Lee ◽  
Irving B. Fritz
Keyword(s):  
Rat Liver ◽  
Ketone Body ◽  
Liver Mitochondria ◽  
Metabolic Inhibitors ◽  
Rat Liver Mitochondria ◽  
Acetyl Coa ◽  
Body Formation ◽  
Mitochondrial Fractions ◽  
Chain Acyl ◽  
Long Chain

Factors controlling the rates of ketogenesis by intact rat liver mitochondria have been investigated. High rates of ketone body formation were obtained with (−)-palmitoylcarnitine (20–120 μM) as substrate, but much lower rates were observed when pyruvate (0.33–1.66 mM) or (−)-acetylcarnitine (0.33–1.00 mM) was substrate. Concentrations of CoA-SH, acetyl-CoA, and long-chain acyl-CoA have been determined in mitochondria incubated with each of these substrates in the absence of metabolic inhibitors. In general, rates of ketogenesis increased as CoA-SH levels fell. Although acetyl-CoA concentrations increased in mitochondria incubated in the presence of low concentrations of (−)-palmitoylcarnitine (below 40 μM), they decreased when higher concentrations of (−)-palmitoylcarnitine were employed. This lowering of acetyl-CoA levels occurred concomitantly with an increase in concentrations of long-chain acyl-CoA and a decrease in CoA-SH levels.In soluble mitochondrial fractions obtained after sonication, CoA-SH addition inhibited acetoacetate formation. The ratio of [acetyl-CoA]/[CoA-SH] and the concentrations of CoA-SH were shown to be of greater importance in the regulation of ketogenesis than was the concentration of acetyl-CoA. Additional factors controlling rates of ketogenesis are discussed in relation to data presented. For example, the [acetyl-CoA]/[CoA-SH] ratio was considerably elevated when pyruvate or (−)-acetylcarnitine was substrate, but at such ratios the rates of ketogenesis were far lower than when (−)-palmitoylcarnitine was the substrate. It was calculated that the "apparent Km" of acetoacetyl-CoA for ketone body formation in intact rat liver mitochondria was approximately 10−9 M when (−)-palmitoylcarnitine was the substrate but it was significantly higher when (−)-acetylcarnitine and pyruvate were substrates.

Effect of Riboflavin Deficiency on the Metabolism of Oxypurines in Chicks

1971 ◽  
Vol 49 (12) ◽  
pp. 1059-1062 ◽  
Author(s):  
S. T. Chou
Keyword(s):  
Uric Acid ◽  
Acid Synthesis ◽  
Xanthine Dehydrogenase ◽  
Broiler Chicks ◽  
Uric Acid Concentration ◽  
Riboflavin Deficiency ◽  
Deficient Diet ◽  
High Incidence ◽  
Liver And Kidney ◽  
Riboflavin Deficient

Day-old broiler chicks of both sexes were used in three experiments to determine the effect of riboflavin deficiency on oxypurine metabolism catalyzed by xanthine dehydrogenase, a riboflavin-containing enzyme. Chicks fed a riboflavin-deficient diet (1.38 mg/kg) for 3 weeks exhibited depressed growth and a high incidence of curled-toe paralysis (higher than 80%) as compared to control chicks (15.1 mg riboflavin per kilogram diet; no incidence of curled-toe paralysis). In addition, the precursors of uric acid, hypoxanthine and/or xanthine, accumulated in the liver and kidney of deficient chicks showing curled-toe paralysis. These observations show that dietary riboflavin being incorporated into xanthine dehydrogenase is essential for oxypurine metabolism. Moreover in the chick, the liver and the kidney may be important sites of uric acid synthesis. The low uric acid concentration in the plasma of the deficient chicks appeared to be indicative of a disturbance in uric acid synthesis in the liver and kidney.

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