Eva Walaas

Spectrophotometric and electron-spin resonance studies of complexes of catecholamines with Cu(II) ions and the interaction of ceruloplasmin with catecholamines

Abstract The complex formation of catecholamines with Cu(II) ions, and their interaction with the copper-containing enzyme ceruloplasmin, have been investigated, with special emphasis on complex formation in the absence of oxygen. In argon, stable 1:2 copper(II)ion-catecholamine complexes with definite optical properties have been observed. The electron-spin resonance (ESR) absorption spectra of these complexes in solution have been recorded. They exert the same characteristics as described for Cu(II) complexes with small molecules in general. Introduction of oxygen initiates the transformation of the catecholamines to the corresponding indolic structures, the adrenochrome, and the noradrenochrome, with characteristic optical properties. The ESR absorption spectra of the complexes are retained in the oxygen-containing solution, but the hyperfine structure is diminished. The interaction of catecholamines with ceruloplasmin in the absence of oxygen is characterized by the disappearance of the 605 mμ absorption band. At the same time the ESR signal of ceruloplasmin completely disappears. Introduction of oxygen reactivates the enzyme and promotes oxidation of the ligand. Simultaneously the ESR absorption spectrum of the enzyme partly reappears. A cupric-cuprous couple has been indicated for the mechanism of enzyme action. The mechanism of electron transfer during oxidation of catecholamines by the model complexes and by ceruloplasmin has been discussed.

Oxidation of reduced phosphopyridine nucleotides by p-phenylenediamines, catecholamines and serotonin in the presence of ceruloplasmin.

Abstract Oxidation of reduced diphosphopyridine nucleotide and triphosphopyridine nucleotide has been obtained by a system containing ceruloplasmin and an appropriate substrate. Among the substrates investigated, p -phenylenediamine, N,N -dimethyl- p -phenylenediamine, and 3,4-dihydroxyphenylhydroxyethylamine (noradrenaline) gave the highest rate of oxidation. The N -methyl-substituted 3,4-dihydroxyphenylhydroxyethylamine (adrenaline) showed definitely lower activity, and 5-hydroxyptamine (serotonin) was slightly active. It is indicated that two steps are involved in the reaction. First, free radicals of the substrates are formed as a result of ceruloplasmin activity. Secondly, the radicals oxidize reduced phosphopyridine nucleotides by acting as “one-electron acceptor” agents. These conclusions are based upon experiments where the absorption spectra of substrates and ceruloplasmin during enzymic activity have been investigated. It has been demonstrated that the intensity of the absorption band with maximum at 605 mμ in ceruloplasmin is decreased by the substrates. This indicates a reduction of the Cu 2+ atoms of the enzyme during catalytic activity.

A stimulatory effect of insulin on phosphorylation of a peptide in sarcolemma-enriched membrane preparation from rat skeletal muscle

It has been well established that insulin stimulates glycogen and lipid synthesis by influencing protein phosphorylation of some of the enzymes involved in these processes. Three different mechanisms for the insulin effect on phosphorylation of enzymes in the cytosol have been proposed. These involve: (i) Decreased cyclic AMP-dependent protein kinase activity [ 1,2] . (ii) Inhibition of a newly discovered protein kinase which is independent of cyclic AMP (3). (iii) Activation of protein phosphatase [4] . An insulin effect by any of these mechanisms would lead to dephosphorylation of certain metabolic enzymes. On the other hand we have previously demonstrated that insulin promotes increased turnover of 32P in y-phosphate of ATP in muscle [S] . In light of these observations we have now investigated the possibility that insulin might influence protein phosphorylations at the level of the plasma membrane. For this purpose we have studied a sarcolemma enriched membrane preparation from rat skeletal muscle. This membrane preparation has been isolated by a mild procedure where treatment with high salt concentrations has been avoided. Protein phosphorylation of this membrane preparation has been investigated and it has been demonstrated that insulin specifically itimulates phosphorylation of a membrane peptide of lower molecular weight. 2. Methods

The influence of sodium, potassium and lithium on the response of glycogen synthetase I to insulin and epinephrine in the isolated rat diaphragm

Abstract 1. 1. Intact rat hemidiaphragms were incubated in media of different ionic composition in the absence and the presence of hormones i.e. insulin and epinephrine. After incubation, glycogen synthetase activity of diaphragm extracts was determined in the absence (I-form) and the presence of glucose 6-phosphate (D-form). 2. 2. Incubation of the diaphragms in media of high K+ concentration led to decreased glycogen synthetase I levels. The response of the synthetase system to insulin (conversion of the D-form to the I-form) was reduced under these conditions. Furthermore, the conversion of the I-form to the D-form of glycogen synthetase promoted by epinephrine was also reduced. 3. 3. Incubation of the diaphragm in lithium-containing media increased glycogen synthetase I. Insulin and lithium exerted additive effects in promoting D to I conversion of the synthetase. 4. 4. The response of glycogen synthetase of the diaphragm to insulin (conversion of the D-form to the I-form) was markedly reduced when (Na+-K+)-activated ATPase was blocked by 0.2 mM ouabain in the incubation medium. 5. 5. The insulin effect on glycogen synthetase was absent when active Na+ and K+ transport was blocked by incubation in a medium lacking K+. This was shown by: (a) incubation of the diaphragm in a K+-free medium to which tetraphenylboron, a K+-chelating agent, was added. (b) removal of K+ by preliminary soaking of the diaphragm in a medium containing Dowex 50 WNa. 6. 6. The response of glycogen synthetase to epinephrine was not affected by incubation of the diaphragm in a K+-free medium.

Interaction of dimethyl-p-phenylenediamine with ceruloplasmin

The stoichiometric interaction of dimethyl-p-phenylenediamine (DPD) with ceruloplasmin-Cu2+ has been investigated by spectrophotometric and electron paramagnetic resonance technique. Intermediates in the reaction sequence, DPD → (DPD)+ → (DPD)2+ → further oxidation products, were characterized. Cerulo-plasmin-Cu2+ was rapidly reduced by DPD as well as by the monoradical ion (DPD)+ but not by (DPD)2+. The two oxidation products (DPD)+ and (DPD)2+ were reversibly reduced by NADH2. The stoichiometry of the reactions confirmed that DPD is oxidized by one electron transfer to ceruloplasmin-Cu2+ in two subsequent steps. Calculations of some of the rate constants were done. The “association constant” k1 for DPD with ceruloplasmin was 750m−1 sec−1, and k′1 for (DPD)+ 800m−1 sec−1 at 10 °. The rate constant for the reoxidation of ceruloplasmin-Cu+ was 0.037 sec−1. When DPD was oxidized by ceruloplasmin, the formation of a relatively stable protein-bound radical was indicated. Kinetic studies of the oxidation of DPD by ceruloplasmin in catalytical amounts were done. The results suggested two different types of active sites or oxidizing units in ceruloplasmin.

The effect of insulin and guanosine nucleotides on protein phosphorylations by sarcolemma membranes from skeletal muscle

In a previous report we have shown that insulin increases the phosphorylation of an endogenous protein of mol. wt. 16 000 daltons in sarcolemma membranes. In the present work we have demonstrated that phosphorylations of exogenous histones by the sarcolemma membranes are also increased by insulin. These results indicate that insulin activates a cyclic-AMP-independent protein kinase in sarcolemma membranes. The stimulatory effect of insulin on protein phosphorylations is increased by GTP and its analogue GMP-P(NH)P. The insulin effect was increased 3--4-fold by micromolar concentrations of GTP. The effect by the analogue GMP-P(NH)P was somewhat less. In the absence of insulin guanosine nucleotides had no effect on phosphorylation of the proteins. The results suggest that GTP is a modulator in the activation of a sarcolemma membrane protein kinase by insulin.

The effect of noradrenaline and adrenochrome on carbohydrate metabolism of rat diaphragm

Abstract 1. 1. Noradrenaline in vitro produced an inhibition of glycogen synthesis and glucose uptake in the diaphragm, i.e the same effects at those produced by adrenaline. The relative biological activity of l -adrenaline, l -noradrenaline and d , l -noradrenaline was 1:1/4:1/10. This is a situation corresponding to that known for the glycogenolytic effect of these substances in the liver. 2. 2. Adrenaline “protected” against oxidation by glutathione gave the same metabolic effects in the diaphragm as “unprotected” adrenaline. Adrenochrome has no metabolic effects on the diaphragm in vitro . 3. 3. In saline phosphate medium, pH 7.4 at 37°C, adrenaline was rapidly oxidized to adrenochrome. This conversion was inhibited by glutathione or by addition of diaphragm to the incubation medium. 4. 4. Hexokinase activity in extracts of rat diaphragm was sensitive to sulfhydryl agents Adrenochrome inhibited hexokinase activity probably by reversible oxidationof sulfhydryl groups. 5. 5. The experiments indicate that the physiological effects of adrenaline on carbohydrate metabolism in muscle is due to the adrenaline molecule as such.

ABNORMAL EFFECTS OF PREALBUMIN FROM SERA OF PSYCHOTIC PATIENTS ON METABOLISM OF RAT DIAPHRAGM

It has earlicr been demonstrated that glucose uptake in rat diaphragm is inhibited by sera from schizophrenics (WALAAS, LINGJBRDE et al. 1954). This effect could be attributed to an inhibitory effect by a,-globulin fraction from sera of these patients on glucose uptake in rat diaphragm. (HAAVALDSEN, LINGJBRDE & WALAAS, 1958). I n extensive studies FROHMAN, GOTTLIEB, BECKETT and coworkers a t The Lafayette Clinic, Detroit, have shown that a,-globulin fractions from sera of schizophrenics influences glycolysis of chicken erythrocytes (FROHMAN, GOODMAN, BECKETT, LATHAM, SENF & GOTTLIEB, 1962). I n the present communication it has been reported that prealbumin isolated on starch block electrophoresis from sera of schizophrenic and other psychotic patients influences the metabolism of rat diaphragm. It has been shown that prealbumin from these patients markedly inhibits glycogen synthesis, incorporation of 1%-glucose into glycogen and incorporation of 14C-phenylalanin in proteins of rat diaphragm. This means that the abnormal serum prealbumin inhibits glycogen synthesis as well as protein synthesis in vitro. No such effects of serum prealbumin from normal individuals have been observed. The abnormal multimetabolic effects of prealbumin to a great extent disappeared upon treatment of the patients with chlorpromazine. We consider the abnormalities in serum protein fractions which have been demonstrated may be responsible for abnormalities in carbohydrate metabolism seen in schizophrenia (LINGJXRDE, 1964), and may also be related to psychotic exacerbations in the disease. A report on these investigations will appear elsewhere.

Plasma pre-α-lipoproteins in ethionine induced fatty liver in rats

Nach Ethionin-Behandlung wird im Rattenplasma eine Reduktion des Pre-α-Lipoproteins festgestellt.