Norbert Katz
University of Freiburg
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FEBS Letters | 1977
Norbert Katz; Harald F. Teutsch; Kurt Jungermann; Dieter Sasse
Liver and kidney catalyze glycolysis as well as gluconeogenesis [l-3] . In isolated liver cell suspensions the antagonistic processes were shown to occur simultaneously, the net process being dependent on substrate concentrations [4]. This mode of action of liver cells and the histochemicaily determined heterogeneous distribution of glucose-6-phosphatase (G6Pase) [5] and of glycogen metabolism [6,7] between periportal+ and perivenous+ zones of liver parenchyma led to the proposal of a metabolic zonation of the organ [4,5 ] . It was suggested that in the peripcrtal zone glucose formation by gluconeogenesis and glycogenolysis might be the predominant process, while in the perivenous zone glycolysis linked to liponeogenesis should prevail. Such a zonation would be analogous to kidney cortex heterogeneity, gluconeogenesis being located in the proximal and glycolysis in the distal tubules [9-l I]. The concept of a metabolic zonation of liver parenchyma was then further strengthened by demonstrating with the microdissection technique [ 121 that the glucogenic enzymes phosphoenolpyruvate carboxykinase [ 131 and glucose-6-phosphatase [ 141 were predominantly located in the periportal and the glycolytic pyruvate kinase [ 131 in the perivenous zone.
FEBS Letters | 1975
Dieter Sasse; Norbert Katz; Kurt Jungermann
It has been observed recently that rat hepatocyte suspensions catalyze glycolysis and gluconeogenesis simultaneously [ 11. The simultaneous catalysis of the two antagonistic processes may occur in one and the same hepatocyte or, as has been proposed [ 11, in two different types of hepatocytes, one catalyzing glycolysis the other gluconeogenesis. The key enzyme for the differentiation of such two hypothetical types of hepatocytes is glucose-6-phosphatase; only the cells possessing this enzyme will be able to release glucose and hence be “gluconeogenic”. In the present study it is shown that in the rat Liver parenchyma zones with high and low activities of glucose-6-phosphatase, glycogen synthase and.glycogen phosphorylase can be differentiated and that this differentiation is preserved in isolated single hepatocytes. The glucose-6-phosphatase-rich zone is always located around the portal branches; its relative size is subject to dietary changes. The observed doubling of the glucose-6-phosphatase level in the liver upon starvation appears to be due to both an increase in the number of glucose-6-phosphatase-rich liver cells and a rise in enzyme level within the already enzyme-rich hepatocytes.
FEBS Letters | 1977
Norbert Katz; Harald F. Teutsch; Dieter Sasse; Kurt Jungermann
Liver and kidney catalyze glycolysis as well as gluconeogenesis [l-3] . In the rat nephron these two antagonistic processes are spatially separated between proximal and distal tubules, as could be demonstrated by studies of enzyme activities in microdissected kidney tissue [4-61. In rat liver parenchyma the two pathways might also be catalyzed in different cells, which would best explain the simultaneous catalysis of glycolysis and gluconeogenesis observed [7,8] . Histochemical studies of liver parenchyma showed a heterogeneous distribution of glucose-6-phosphatase (G6Pase). It was proposed that in the G6Pase-rich periportal* zone glucose formation by gluconeogenesis and glycogenolysis should be catalyzed, while in the G6Pase-poor perivenous* zone glycolysis may be the predominant process [9]. Histochemical enzyme determinations mostly provide only a qualitative or at best a semiquantitative information. Therefore, a quantification of histochemi cal findings appeared desirable. In the present investigation G6Pase was quantitatively determined by direct enzyme measurement in periportal and perivenous liver tissue separated by microdissection. It was found that the G6Pase activity of fed animals was about 2.3-fold higher and of fasted animals about 1.7-fold higher,in zone 1 than in zone 3. This finding supports the theory of a ‘metabolic zonation’ of liver parenchyma into functionally different hepatocytes [7-91.
Biochemical and Biophysical Research Communications | 1979
Norbert Katz; Michael A. Nauck; Paul T. Wilson
Abstract Glucokinase, the organ specific key enzyme of glucose metabolism in liver, was studied in primary cultures of adult rat hepatocytes during the first two days after cell preparation. In the presence of dexamethasone low concentrations of insulin (10 −9 mol/l) prevented the observed time dependent decrease of glucokinase activity while higher insulin concentrations (10 −8 and 10 −7 mol/l) led to a twofold increase of enzyme activity. The enhancement of glucokinase activity was completely blocked by either actinomycin D or cycloheximide. The degree of this insulin dependent induction was correlated with the concentration of added dexamethasone, which seemed to perform a permissive function. The induction of glucokinase activity could be prevented by addition of glucagon (2 × 10 −7 mol/l).
Biological Chemistry | 2003
Nadia Al-Fakhri; Triantafyllos Chavakis; Thomas Schmidt-Wöll; Bei Huang; Sanjay Mammen Cherian; Yuri V. Bobryshev; Reginald S. A. Lord; Norbert Katz; Klaus T. Preissner
Abstract Plasminogen activator inhibitor-1 (PAI-1) and twochain high molecular weight kininogen (HKa) exert antiadhesive properties in vitronectindependent cell adhesion. Here, the hypothesis was tested that these anti-adhesive components promote apoptosis in vascular cells. PAI-1 or HKa induced a 2- to 3-fold increase in apoptosis of human umbilicalvein endothelial cells (HUVEC) and vascular smooth muscle cells (VSMC) adherent to vitronectin, as determined by annexin VFACS assay, similar to αvintegrin inhibitor cyclo-(Arg-Gly-Asp-D-Phe-Val)-peptide (cRGDfV). Apoptosis occurred after 12 h incubation and was attributable to caspase 3 activation that in turn induced DNA fragmentation. Induction of apoptosis strongly correlated with the antiadhesive effect of PAI-1 and HKa on these cells. In contrast, PAI-1 and HKa did not affect fibronectin-dependent adhesion or cell survival. uPA did not influence apoptosis in vitronectin- or fibronectin-adherent cells. In atherosclerotic vessel sections, congruent distribution of vitronectin, PAI-1, HK, and of components of the urokinase plasminogen activator/receptor system with apoptotic cells lining foam cell lesions was demonstrated by immunostaining. These results indicate that inhibition of vitronectindependent cell adhesion through PAI-1 and HKa correlates with apoptosis induction in vascular cells mediated through the caspase 3 pathway. Co-distribution of apoptosis with plasminogen activation system components in atherosclerosis exemplifies the significance of antiadhesive mechanisms and apoptosis for tissue remodeling, such as in neointima development.
FEBS Letters | 1976
Norbert Katz; Harald F. Teutsch; Kurt Jungermann; Dieter Sasse
Adult liver catalyzes the antagonistic processes gluconeogenesis and glycolysis [l] . The heterogeneous distribution of glucose-6-phosphatase (G6Pase) over the liver parenchyma of the rat [2,3] and mouse [4] was interpreted to indicate a metabolic zonation of the liver lobule with respect to carbohydrate metabolism [5,6]. In the G6Pase-rich periportal zone glucose should be formed from gluconeogenesis and glycogenolysis. In the G6Pase-poor pericentral zone glycolysis may be the predominant process [7].. This metabolic zonation is influenced by changes of the nutritional state [S] . Prenatal liver parenchyma appears to catalyze only glycolysis [8,9], it should thus not be metabolically zonated. It was, therefore, of interest to study the perinatal development of the metabolic zonation and to try to correlate it with the drastic alteration of the nutritional state occurring with birth and during the following neonatal period. In the present study the following results have been obtained: (1) G6Pase is absent from prenatal liver. It appears rapidly in a homogeneous distribution with birth. From the 3rd or 4th postnatal day the zonation of G6Pase begins to develop; it is completed around the 12th day. (2) Glycogen storage begins 3 days before birth; it reaches a maximum with a homogeneous distribution at birth. Glycogen breakdown occurs rapidly during the first postnatal days predominantly in the G6Pase-rich zones. (3) Both the development of the zonation of G6Pase and of glycagen can be correlated to the perinatal switch from carbohydrateto proteinplus fatand back to carbohydrate-rich nutrition.
Journal of Cancer Research and Clinical Oncology | 1987
Gösta Fischer; Ilka Ruschenburg; Erich Eigenbrodt; Norbert Katz
SummaryPreneoplastic liver lesions were produced in female Wistar rats by oral administration of 2-acetyl-aminofluorene for 165 days succeeded by a carcinogen-free standard diet up to 420 days. During the treatment numerous altered hepatic foci (AHF) and hyperplastic nodules (HN) were detected histochemically by a focal decrease or lack of adenosine-5-triphosphatase and glucose-6-phosphatase (G-6-Pase) activities. In addition, the immunohistochemically demosntrable amount of L-type pyruvate kinase was clearly reduced. The histochemically demonstrated decrease of G-6-Pase was substantiated by microbiochemical determination of the enzyme activity in microdissected material. Moreover, during the experimental period a continuous decrease in glucokinase and an increase in hexokinase was detected microbiochemically within AHF and HN. These alterations indicate, a shift in the carbohydrate metabolism from gluconeogenesis to glucose utilization and pentose-phosphate-pathway for biosynthesis of nucleic acids. Beside other oncofetal markers, HK may be used as indicator of the early stages of liver carcinogenesis.
FEBS Letters | 1991
Karl H. Reuner; Kurt Schlegel; Ingo Just; Klaus Aktories; Norbert Katz
ADP‐ribosylation of actin by Clostridium botulinum C2 toxin resulted in a depolymerization of filamentous F‐actin and an increase of monomeric G‐actin in cultured hepatocytes, Simultaneously the de novo synthesis of actin was largely reduced, while the synthesis of albumin and of other proteins was not significantly impaired. The specific decrease of actin mRNA to 30% of the control indicates a down‐regulation of actin synthesis at a pretranslational level. On the other hand, treatment with the mycotoxin phalloidin resulted in an increase of F‐actin and a decrease of monomeric G‐actin. Under this condition the de novo synthesis of actin was specifically enhanced and the level of actin mRNA was increased to 600% of the control. The data suggest an autoregulatory control of the actin synthesis.
Alcohol and Aldehyde Metabolizing Systems#R##N#Intermediary Metabolism and Neurochemistry | 1977
Kurt Jungermann; Norbert Katz; Harald F. Teutsch; Dieter Sasse
With hepatocyte suspensions it was found that (a) in the C3 part of carbohydrate metabolism glycolysis can be shifted to gluconeogenesis, dependent only on substrate concentrations rather than on hormones, and that (b) in both the C6 and C3 part glycolysis and gluconeogenesis are catalyzed simultaneously. This mode of action of the liver led to the hypothesis that there are at least two types of metabolically different hepatocytes forming a gluconeogenic and a glycolytic organ zone. Histochemical studies and biochemical analysis after microdissection of liver tissue indicated that the key glucogenic enzyme glucose-6-phosphatase (G6Pase) is highly active in periportal, and hardly active in perivenous hepatocytes, and that in the post-absorptive period glycogen is degraded first in the G6Pase rich cells. These results together with findings reported by other investigators support the model of “metabolic zonation” of liver parenchyma.
FEBS Letters | 1974
Kurt Jungermann; H. Kirchniawy; Norbert Katz; Rudolf K. Thauer
Clostridial nitrogenase catalyzes the ATP dependent reduction of Ns to NHs with reduced ferredoxin as electron donor [l] . In cell-free extracts of N,-grown Clostridium pasteuriunum several systems have been used to regenerate the reduced ferredoxin required in the nitrogenase reaction: pyruvate and pyruvate-ferredoxin oxidoreductase [2] , hydrogen and hydrogenase [3] as well as formate and COZreductase [4]. Therefore pyruvate, hydrogen and formate are generally regarded as the physiological reductants in clostridial nitrogen fixation [5,6]. NADH has also been reported to reduce ferredoxin via a NADH-ferredoxin oxidoreductase in several clostridia, which were however NHs-grown and thus devoid of the nitrogenase system [7-lo]. Since the NADH-ferredoxin oxidoreductase has not been demonstrated in Ns-grown clostridia as yet, NADH does not appear to be accepted as an electron donor for clostridial Ns-reduo tion, although this was indicated by preliminary evidence [3] and theoretical considerations [l I]. In this communication it is shown that NADHferredoxin oxidoreductase is present also in cellfree extracts of Ns-grown Cl. pasteurianum and