Amino acids and lipoproteins in plasma of duodenopancreatectomized patients: effects of glucagon in physiological amounts.

Duodenopancreatectomy induces a severe glucagon deficiency and elevated plasma concentrations of alanine, aspartate, glycine, proline, serine, arginine, citrulline, ornithine, phenylalanine and tyrosine. Restoring high physiological plasma glucagon in six such patients by infusing 0.3 mg/24 h of exogenous glucagon reduced significantly (P less than 0.01 or 0.001) the mentioned amino acids (except phenylalanine) and further asparagine, glutamine, methionine and threonine. In six normal subjects the same infusion reduced significantly (P less than 0.05 to 0.001) plasma alanine, asparagine, glutamate, glutamine, glycine, proline, serine, threonine, arginine, ornithine, lysine and tyrosine. However, the effect was significantly (P less than 0.01 or 0.001) less marked for alanine, glutamine, glycine, methionine, serine, threonine and arginine. This particular glucagon sensitivity of duodenopancreatectomized patients suggests that glucagon deficiency is the cause of their hyperaminacidaemia. By contrast, lipoprotein concentrations were virtually unaffected by either glucagon deficiency or its replacement. In the light of the marked hypoaminacidaemia in glucagonoma patients these results attribute to glucagon a major role as a regulator of protein metabolism.

In vitro and in vivo studies on glucagonoma tissue.

A 66 year old patient with diabetes had a necrolytic migratory erythema, weight loss and anaemia. Plasma immunoreactive glucagon (IRG) of 2465 pmoles/l (normal 35 +/- 5 SEM pmoles/l) suggested the existence of a glucagonoma which was confirmed by arteriography and subsequently removed by surgery. Although plasma IRG returned to normal, glucose tolerance and insulin secretion remained pathological. Plasma amino acid levels had been reduced but were corrected by surgery. Pancreatic polypeptide, however, 298 pmoles/l before was still 206 pmoles/l after the operation (normal 12-48 pmoles per litre). Column chromatography of plasma and tumor extracts showed quantitatively important IRG fractions with molecular weights above 9000 daltons, possibly precursors of glucagon. Beside a 50-fold IRG excess, the tumour concentrations of insulin and somatostatin were 4 to 150 times increased. By contrast, pancreatic polypeptide was present in normal amounts. Electron microscopic examination showed atypical A-cell granula and unusual abundance of mitochondria.

Changes in the concentrations of branched chain amino acids in the blood in response to alterations in the composition of a hypocaloric diet.

This report describes an investigation of the effect of an alteration in the amount of protein, carbohydrate and fat in hypocaloric diets on the concentration ratios of valine/(isoleucine + leucine) in the morning fasting blood in healthy men: in some cases the effect of a higher caloric diet was also analysed. During the nutrition periods, each over 10 days, the concentrations of branched chain amino acids and alanine, blood levels of insulin, glucose and free fatty acids and the nitrogen balance were estimated daily. With hypocaloric diets, as well as with hypercaloric diets, supplementation of food protein from 0.6 or 0.8 up to 2.0 g protein per kg body weight (isocalorically) induced a rise of the molar ratios of valine/(isoleucine + leucine) in blood from 0.98 to 1.25 (4600 kJ/d) or 1.06 to 1.45 (14600 kJ/d) respectively. A correlation of molar ratios of valine/(isoleucine + leucine) in the blood and the nitrogen balance could not be established. However, it is suggested that ratios above a limiting value exclude the possibility of a distinct negative nitrogen balance during 7 or 10 days of observation.

Blood amine acid levels in patients with insulin excess (functioning insulinoma) and insulin deficiency (diabetic ketosis).

Blood amino acid concentrations were determined in the postabsorptive state in nine patients with insulin excess (functioning insulinomas), nine juvenile-type diabetics with insulin deficiency (diabetic ketosis due to insulin withdrawal), six juvenile diabetics in moderate metabolic control, and five healthy control subjects. Blood branched-chain amino acid (BCAA) levels were elevated in diabetic ketosis and decreased in patients with insulinomas. Blood concentrations of BCAA were significantly correlated to blood glucose levels, and in diabetics they were also correlated to blood ketone bodies, serum free fatty acids, and glycerol levels. These data indicate an inverse relationship between circulating effective insulin levels and blood BCAA concentrations. It is suggested that blood levels of BCAA might represent an indicator of insulin-dependent alterations of protein metabolism.

Mitochondrial adenosine triphosphatase from yeast, Saccharomyces cerevisiae. Purification, subunit structure and kinetics.

1. A procedure for the purification of ATPase extracted by chloroform from baker's yeast (Saccharomyces cerevisiae) is reported. The yield based on submitochondrial particles was 55% and the purification was 100-fold. The isolated complex was homogenous as assessed by gel filtration, ion-exchange chromatography, sedimentation in sucrose gradient and in the analytical ultracentrifuge. The molecular weight determined by gel filtration was 400000 +/- 20000. Ultracentrifugation yielded s020,w = 12.50 +/- 0.13 S and the laser light scattering study gave a diffusion coeficient of D20w - 2.92 X 10(-7) cm2 s-1. The amino acid composition as well as absorption, fluorescence, and circular dichroism spectra, from which the helicity of 39% was evaluated, are given. 2. On polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, six components with molecular weights of 58500(alpha), 55000 (beta), 42000, 34000 (gamma), 10000(delta), and 8600 (epsilon) were observed with a stoichiometry of 3:3:1:1:1:1. The amino acid composition is given for alpha + beta and gamma as well as delta and epsilon components. 3. The maximum specific activity of the enzyme was 200 U/mg under the optimum conditions. The enzyme was inactivated by incubation at 0 degrees C and strongly inhibited by the antibiotic Dio-9 but not by oligomycin and N, N'-dicyclohexyl-carbodiimide. The effects of kinetic parameters and anions on the enzyme are reported. Two active sites for Mg-ATP with Km values of 0.045mM and 0.37mM and a single activie site for Mg-ITP with Km = 0.179mM were found. A study of the temperature dependence of the maximum activity revealed a straight line in the Arrhenius plots with an activation energy of 11.0 kcal/mol (= 46 kH/mol).

[Relationship between nitrogen balance and amino acids, free fatty acids, glucose and insulin in human blood under various metabolic conditions (author's transl)]. / Beziehungen zwischen Stickstoff-Bilanz und Aminosäuren, freien Fettsäuren, Glucose und Insulin im Blut in verschiedenen Stoffwechselsituationen des menschlichen Organismus

Nutrition experiments with various levels of calorie and protein intake were carried out on five healthy young men. Three series of experiments with two persons each were undertaken for periods up to 14 days. The first part of each experiment, with 1100 to 1500 kcal/day, was immediately followed by the second part, with 3500 to 2300 kcal/day. The concentrations of insulin, free fatty acids, glucose and amino acids were determined in the morning, fasted blood. The nitrogen balance was also determined. When insufficient carbohydrate intake is coupled with normal and high protein content of the food, there is interindividually an initial drop in the insulin concentration. Regardless of the absolute insulin concentration, this drop causes an increase in the free fatty acids and the branched-chain amino acids, together with a decrease in the concentrations of alanine and glycine (threonine) in the blood and a negative nitrogen balance. The high concentrations of branched-chain amino acids and the low threonine concentrations might be involved as feedback regulators in the further regulation of the gluconeogenic metabolism. When carbohydrate calories are added to the diet, a simultaneous decrease in the free fatty acids and branched-chain amino acids and increase in the blood concentrations of insulin, alanine, glycine and threonine within 24 to 48 h are only observed with 3500 kcal/day and 0.8 to 1.4 g protein per kg body weight. A positive nitrogen balance, however, is only observed with 1.4 g protein per kg body weight, regardless of the relative changes in the insulin level, while the increase in alanine and decrease in branched-chain amino acids (valine) are greatest at 0.8 g protein per kg body weight and day. In spite of the high glucose level, the falling insulin level provokes counter-regulatory processes in which the low concentrations of branched-chain amino acids and the high threonine (alanine) concentrations may play a role.

Mechanism of renaturation of pyruvate kinase of Saccharomyces carlsbergensis: activation by L-valine and magnesium and manganese ions.

Pyruvate kinase (EC 2.7.1.40) of S. carlsbergensis is a tetrameric enzyme, composed of four identical subunits each of which contains 1 mole of L-valine noncovalently bound. The enzyme readily dissociates into monomeric units. L-Valine and magnesium or manganese ions are specific primers of the renaturation process of the enzyme. The amino acid induces renaturation with a K(0.5) of 17 muM and a pseudo first-order rate constant of 0.019 min(-1) at 25 degrees with respect to the monomeric species, indicating that L-valine influences the folding of the monomeric form from a disordered state to its native conformation being followed by a spontaneous reassociation with formation of the tetrameric enzyme. Independently, magnesium and manganese ions induce the renaturation with a first-order rate constant of the same magnitude.