Accelerated degradation of adenine nucleotide in erythrocytes of patients with chronic renal failure.

Recently, we have shown that erythrocytes obtained from patients with chronic renal failure (CRF) exhibited an increased rate of ATP formation from adenine as a substrate. Thus, we concluded that this process was in part responsible for the increase of adenine nucleotide concentration in uremic erythrocytes. There cannot be excluded however, that a decreased rate of adenylate degradation is an additional mechanism responsible for the elevated ATP concentration.

Increased rate of adenine incorporation into adenine nucleotide pool in erythrocytes of patients with chronic renal failure.

Background: Elevated purine nucleotide pool (mainly ATP) in erythrocytes of patients with chronic renal failure (CRF) is a known phenomenon, however the mechanism responsible for this abnormality is far from being clear. We hypothesize that the increased rate of adenine incorporation into adenine nucleotide pool is responsible for the elevated level of ATP in uremic erythrocytes.

Methods: In chronically uremic patients we evaluated using HPLC technique: (a) plasma adenine concentration; (b) the rate of adenine incorporation into adenine nucleotide pool in uremic erythrocytes.

Comparative study of the lipogenic potential of human and rat adipose tissue.

The reported low activity of lipogenic enzymes (especially adenosine triphosphate [ATP]-citrate lyase) in human adipose tissue led to the general conclusion that in humans lipogenesis occurs primarily in the liver. However, recent studies indicate that the liver plays a minor role in de novo lipogenesis and suggest that adipose tissue may be the principal lipogenic human tissue. In an attempt to resolve these contradictions we reinvestigated the lipogenic potential of human adipose tissue and compared with adipose tissue of rats fed a high-fat diet for 2 weeks and fasted overnight before death.

Mitochondrial adenosine triphosphatase from human placenta--inhibition by free magnesium ions of ITP hydrolysis.

The effects of Mg2+ and bicarbonate on the kinetics of ITP hydrolysis by soluble ATPase (F1) from human placental mitochondria were studied. Increasing amounts of Mg2+ at fixed ITP concentration, caused a marked activation of F1 followed by inhibition at higher Mg2+ concentration. The appropriate substrate for the mitochondrial F1 seems to be the MgITP complex as almost no ITP was hydrolysed in the absence of magnesium.

Stimulatory effect of ADP, ATP, NAD(P) on pyruvate production from malate by uncoupled human placental mitochondria.

It has been shown that ADP, ATP, NAD(P), and NAD(P)H significantly stimulate pyruvate production from malate by intact uncoupled human term placental mitochondria. No stimulation by ADP was observed when mitochondria were incubated in the presence of NAD(P) or NAD(P)H or when mitochondrial membrane had been disrupted. Atractyloside and oligomycin were without effect on ADP- and ATP-stimulated pyruvate production.

Carboxylation of pyruvate via extramitochondrial malic enzyme in rat skeletal muscle.

Soluble rat skeletal muscle extract incubated in the presence of pyruvate, NaH14CO3, MgCl2 and NADP-generating system fixed H14CO3- at the rate of about 2.3 nmol/min per mg protein. The omission of pyruvate or NADPH-generating system abolished completely the fixation of H14CO3-.

Malic enzymes of salmon trout heart mitochondria: separation and some physicochemical properties of NAD-preferring and NADP-specific enzymes.

Mitochondria isolated from the heart of the Baltic salmon trout Salmo trutta contain two distinct malic enzymes. One of these enzymes (NAD-preferring malic enzyme) catalyses the oxidative decarboxylation of malate in the presence of either NAD or NADP. The specific activity with NAD was six times that with NADP as coenzyme.

Mitochondrial adenosine triphosphatase from human placenta--effects of adenylyl and guanylyl imidodiphosphate.

The effects of adenylylimidodiphosphate (AMP-PNP) and guanylylimidodiphosphate (GMP-PNP) on the kinetics of MgATP, MgITP and MgGTP hydrolysis by mitochondrial ATPase (EC 3.6.1.

Evidence for the role of malic enzyme in the rapid oxidation of malate by cod heart mitochondria.

Mitochondria isolated from the heart of cod (Gadus morrhua callarias) oxidized malate as the only exogenous substrate very rapidly. Pyruvate only slightly increased malate oxidation by these mitochondria. This is in contrast with the mitochondria isolated from rat and rabbit heart which oxidized malate very slowly unless pyruvate was added.

Intracellular distribution of fumarase in rat skeletal muscle.

The distribution of fumarase activity between the mitochondrial and cytoplasmic compartments of rat skeletal muscle was studied using the method of Fatania and Dalziel (Biochim. Biophys. Acta 631 (1980) 11-19), fractional extraction technique and a method based on the calculation of mitochondrial protein content in the tissue and on the determination of fumarase activity both in the tissue homogenate and in the isolated mitochondria.

Isolation and regulatory properties of mitochondrial malic enzyme from rat skeletal muscle.

Mitochondrial malic enzyme (L-malate:NADP+ oxidoreductase (oxalo-acetate-decarboxylating), EC 1.1.1.

Mitochondrial adenosine triphosphatase from human placenta--purification and catalytic properties.

1. The purification of ATPase (EC 3.6.

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.

Effect of some glycolytic intermediates and palmitoyl-CoA on alpha-glycerophosphate dehydrogenase in mitochondria isolated from liver of triiodothyronine-treated rats.

alpha-Glycerophosphate dehydrogenase (EC 1.1.99.

High activity of NADP-dependent malic enzyme in mitochondria from abdomen muscle of the crayfish Orconectes limosus.

1. Mitochondria isolated from abdomen muscle of crayfish Orconectes limosus exhibit malic enzyme activity in the presence of L-malate, NADP and Mn2+ ions after addition of Triton X-100. Under optimal conditions about 230 nmole of reduced NADP and an equivalent amount of pyruvate are produced per min per mg of mitochondrial protein.

Regulation of alpha-glycerophosphate dehydrogenase activity in human term placental mitochondria.

1. alpha-Glycerophosphate dehydrogenase (sn-glycerol-3-phosphate:(acceptor) oxidoreductase, EC 1.1.

High activity of alpha-glycerophosphate oxidation by human placental mitochondria.

Human term placental mitochondria oxidize alpha-glycerophosphate at an unusually high rate as compared to other substrates. The apparent Km both for oxidation and alpha-glycerophosphate dehydrogenase (EC 1.1.

Inhibition of pyruvate oxidation by skeletal muscle mitochondria by phenylpyruvate.

1. Phenylpyruvate inhibits pyruvate plus malate oxidation in human and rat skeletal muscle mitochondria in state 3 and in the uncoupled state, it has, however, no effect in state 4. 2.

Stimulation of citrate oxidation and transport in human placental mitochondria by L-malate.

1. Citrate was oxidized by human placental mitochondria at a rate half that for isocitrate, and cis-aconitate at a rate by 20% lower as with isocitrate. The apparent Km values for these substrates were similar.