Phosphofructokinase isozymes of Morris hepatomas

The spin-lattice relaxation rate of solvent protons in suspensions of chloroplast thylakoid membranes undergoes a large transient depression following illumination in white light. This change appears to require the presence of chelatable paramagnetic ions; it is absent in chloroplasts exposed to 1 mm EDTA during the homogenization step of the isolation procedure, but reappears when 50 μm MnCl₂ is added to these suspensions. Conditions that inhibit light-induced R₁ changes are (i) anaerobiosis, (ii) inhibition of plastocyanin function byHg⁺²/CN, and (iii) the presence of superoxide dismutase. These observations suggest that chemical oxidation of nonfunctional Mn (II) by superoxide ion, which is generated under aerobic conditions by autooxidizable acceptors of Photosystem I, is responsible for the phenomenon. This interpretation was confirmed by experiments involving superoxide generation in the dark, using the NADPH-driven diaphorase activity of ferredoxin-NADP-reductase with benzylviologen as an autooxidizable acceptor.     

Phosphofructokinase isozymes from human organs and blood cells.

Phosphofructokinase (PFK) isozymes of blood cells and some human tissues were studied by starch gel electrophoresis and immunoprecipitation by anti-muscle and anti-erythrocyte PFK sera. PFK from muscle, heart, brain and placenta were totally precipitated by both antisera. PFK from blood cells (erythrocytes, lymphocytes, granulocytes, platelets) were precipitated more strongly by anti-erythrocyte PFK serum than by anti-muscle PFK serum. Liver, kidney and monoblast PFK were slightly precipitated by both antisera. From the electrophoretic patterns and the immunoprecipitation curves we may conclude that muscle contains the homotetrameric M4 forms; platelet, liver and kidney the homotetrameric E4 form, and blood cells the M-E hybrids. Monoblasts probably contain a E4 type PFK precursor, and heart, placenta and brain, a modified M4 type PFK. Other isozymes, unrelated with muscle and erythrocyte, were revealed in liver and kidney.     

Phosphofructokinase (isozymes) activation by theophylline or by 3',5' cyclic AMP administration.

Phosphofructokinase activity of rat thyroid, kidney and muscle can be enhanced by in vivo administration of theophylline or cyclic AMP. This enhancement occurs in the different tissues to a different extent depending on the tissue-specific isozymes. Thyroid and muscle phosphofructokinase which is mainly A-type, is strongly stimulated after administering theophylline in the drinking water over a 8 days period. The kidney enzyme which encompasses about 50% of each A and B type is activated to a lesser extent. Liver phosphofructokinase which is pure B-type shows very little response if any. Comparable results have been obtained with either the muscle or liver enzyme after two to four hours treatment with a single injection of 10 mg/rat of either cyclic AMP or theophylline. This short-term activation could be eliminated by treating the animals with Actinomycin D, 30 min prior to theophylline or cyclic AMP. The possible mechanisms leading to the enhancement of phosphofructokinase activity are discussed.     

Pyruvate kinase isozymes in man

Anti human M2 type and anti human L type pyruvate kinase sera allowed us to distinguish two groups of pyruvate kinase in man. Erythrocyte and liver (L type) enzymes on the one hand were inhibited by anti L and not all by anti M2 serum; pyruvate kinase from all the other tissues on the other hand were inhibited by anti M2 and not at all by anti L serum. This latter group represent the M type pyruvate kinase isozymes. The M type isozymes have been studied by electrofocusing in thin layer acrylamide-ampholine gel. In adult tissues 4 types of isozymes were found, designated, from acid to alkaline pH, as M2 (predominant form in spleen, leukocytes, lung...), M3, M4 and M1 (predominant form in muscle and brain). In foetal tissues an extra band M2, called M2f, more anodic than M2, was added to the previously described isozymes. Except in brain (in which the isozymes M2, M3, M4 and M1 were found), the most anodic bands (M2f, M2 and M3) were predominant in all the foetal tissues. The isozymes M2f and M2 seem therefore to be the original M type pyruvate kinase forms from which the other isozymes issue. The rate of each isozyme seems to depend on tissue factors characterizing the state of differentiation of some tissues, as indicated by the ability of adult muscle extracts to change the isozymes M2 and M3 into more cathodic forms.     

Pyruvate kinase isozymes in man

Summary By focusing in sucrose, gradient L-type pyruvate kinase from human liver could be separated into 2 major forms (pI 6.28±0.03 and 5.85±0.09) and a minor more acid form (pI5). These different forms could also be detected by focusing in acrylamide-ampholine slab gel. The major forms were interconvertible, the equilibrium being shifted toward the acid form by fructose 1,6-diphosphate and SH reagents, and toward the alkaline form by proteinic factors extracted by ammonium sulphate fractionation from liver extracts and from hemolysates. These factors seemed to be responsible for the stabilization of the liver crude extract enzyme in its alkaline conformation.By acrylamide slab gel electrofocusing, erythrocyte pyruvate kinase from whole hemolysates exhibited a complex pattern composed of at least 3 interconvertible forms. The in vitro aging of the red blood cells and the storage of the hemolysates resulted in a progressive disappearance of the acid forms and in a strengthening of the alkaline form. Partially purified erythrocyte enzyme focused in 2 major bands, interconvertible under the influence of the same factors as those described for L-type pyruvate kinase. Although closely related, the focusing patterns of L-type and erythrocyte-type were never exactly identical.Double immunodiffusion against antihuman L-type serum showed a complete identity reaction between erythrocyte-and L-type pyruvate kinases. Moreover, antihuman M₂-type serum was unable to neutralize erythrocyte pyruvate kinase as well as to change its electrophoretic mobility.Consequently, we conclude that both human erythrocyte-and liver L-type pyruvate kinases existed under several conformers interconvertible under the influence of the same ligands or proteinic factors; erythrocyte-type enzyme seems to include L-type subunit and not M₁- or M₂-type subunits. The erythrocyte- and L-type enzymes, however, are not identical and the nature of the differences between them is discussed.Chargé de recherche INSERM.     

Effects of fasting and insulin on hepatic phosphofructokinase (PFK)

Fasting of susceptible mice for 24 hr led to a sharp decrease of apparent hepatic PFK activity which was increased to near fed levels by incubation of cytosolic fractions with GSH. Incubation of the cytosols with GSSG reduced the PFK to a lower level-(GSSG insensitive activity). The action of insulin was to increase total PFK with a marked increase of the GSSG insensitive activity.     

Phosphofructokinase in the plerocercoids of Schistocephalus solidus (Cestoda:Pseudophyllidea)

Beis I. and Theophilidis G. 1982. Phosphofructokinase in the plerocercoids of Schistocephatus solidus (Cestoda: Pseudophyllidea). International Journal for Parasitology12: 389–393. The Phosphofructokinase from the plerocercoids of Schistocephalus solidus was found to be inhibited by ATP. AMP relieves the ATP inhibition and activates the enzyme. In contrast to mammalian phosphofructokinase, the plerocercoid enzyme does not appear to be sensitive to inhibition by citrate at physiological ATP concentrations. Except for AMP and 3'–5' cyclic AMP no other monophosphate nucleotides were found to activate the enzyme. Succinate, α-ketoglutarate, malate, isocitrate, β-hydroxybutyrate, butyrate, acetoacetate and CoA all inhibit the plerocercoid enzyme at the concentrations tested. The significance of these results in the regulation of glycolysis and the tricarboxylic acid cycle in this parasite is discussed.     

Urinary pepsinogen isozymes: A highly polymorphic locus in man

Summary A genetic analysis of human urinary pepsinogen isozymes is presented. Nine discrete phenotypes were identified in a population survey of 215 unrelated Caucasian individuals. The phenotypes were characterized by differences among the staining intensities of the activated group I pepsinogens, Pg 5, Pg 4, Pg 3, and Pg 2. The genetic studies demonstrated that the codominant expression of four alleles, Pg ^A, Pg ^B, Pg ^C and Pg ^D, at a single genetic locus determined the nine phenotypes identified. Linkage analysis excluded close linkage of the Pg locus with the chromosome 6 markers HLA, GLO ₁, and Bf.     

Development of phosphogluco-isomerase isozymes in perennial ryegrass (Lolium perenne)

The development of isozymes of phosphogluco-isomerase (PGI; D-glucose-6-phosphate ketol isomerase EC 5.3.1.9.) in perennial ryegrasses was followed from dry seed through to leaf senescence using starch gel electrophoretic separations. Root isozymes were also examined. Two forms of the enzyme were found, one (PGI/2) being present in all tissues and at all stages of the life cycle. The other (PGI/1) had two zones of activity, one of which was detected only in light-exposed tissue. Normal development of this form could be inhibited by growing seedlings on distilled water. Some alleles of PGI/2 not previously reported for ryegrasses are also described.     

Variation in the isozymes of flax (Linum usitatissimum) genotrophs

Peroxidase, esterase, and acid phosphatase isozymes of environmentally induced L and S genotrophs, nuclear DNA reversion types, and the orginal plastic (Pl) type of the flax variety Stormont Cirrus have been compared by polyacrylamide gel electrophoresis. Differences were observed in particular line was not correlated with the nuclear DNA amount. The relationship between the isozyme pattern and the phenotypes of the lines in which they are expressed is discussed.     

Expression patterns of AMP-deaminase isozymes in human hepatocellular carcinoma (HCC)

Background AMP-deaminase (EC 3.5.4.6) is an enzyme of nucleotide breakdown involved in regulation of energetic metabolism in mammalian cells. The enzyme is coded by a family of three independent genes (AMPD1, AMPD2 and AMPD3), synthesizing three different isozymes. In mammalian liver, the reaction catalyzed by AMP-deaminase constitutes a rate-limiting step in adenine nucleotide catabolism. In neoplastic liver, adenine nucleotide catabolism is a subject of many modifications, which influence the expression of genes synthesizing enzymes regulating this pathway. Aims The experimental studies presented here illustrate the expression of AMPD genes in human liver neoplasm tumor (HCC, hepatocellular carcinoma). Methods RT-PCR and Western blotting methods were used for determining of the goal mentioned above. Results and conclusion Expression level of AMPD gene family in the tumorous fragment (HCC tumor) of neoplastic liver did not differ substantially from that found in the nontumorous (cirrhotic) fragment of the organ. In this case the expression of AMPD2 gene was prevailing. AMPD2 was the main isoform of AMP-deaminase identified in two liver fragments compared. This is a first report evidencing the pattern of AMPD genes expression in neoplastic human liver.     

瑞氏七鳃鳗乳酸脱氢酶（LDH）同工酶凝胶电泳分析

本文用聚丙烯酰胺凝胶电泳方法,对瑞氏七鳃鳗五种不同组织（骨骼肌、心、肾、肠、鳃）中ＬＤＨ同工酶进行了分析研究,结果表明,ＬＤＨ同工酶具有组织特异性,其中骨骼肌中含有五种ＬＤＨ同。酶,即ＬＤＨ１、ＬＤＨ２、ＬＤＨ３、ＬＤＨ４、ＬＤＨ５,鳃含有ＬＤＨ１和ＬＤＨ４而肾和心只含有ＬＤＨ１,肠只含有ＬＤＨ４。