Biotin and glucose metabolism

1970 ◽  
Vol 48 (4) ◽  
pp. 493-500 ◽  
Author(s):  
K. Dakshinamurti ◽  
L. Tarrago-Litvak ◽  
Ho Chong Hong

Biotin enhances liver glucokinase in the diabetic rat. Experiments using inhibitors of protein and RNA synthesis suggest that this is mediated through de novo protein synthesis. Biotin treatment also increases the activities of other key glycolytic kinases, phosphofructokinase and pyruvate kinase, but has no effect on a bifunctional enzyme like phosphohexose isomerase.

1975 ◽  
Vol 2 (2) ◽  
pp. 73-77
Author(s):  
D. L. Ketring

Abstract Control dormant seeds that imbibed water for 16 hr germinated 100% after 10 μ 1/1 C2H4 was applied for 24 hr. Dormant seeds that imbibed cycloheximide (100 μg/ml), 6-methylpurine (50 μ g/ml) and 6-azauracil (50 μ g/ml) for 16 hr did not germinate at either 24 or 48 hr after 10 μ 1/1 ethylene treatment. Both protein- and nucleic acid-synthesis ihhibitors prevented germination induced by ethylene in these dormant seeds. Imbibition of 20 μ M ABA by dormant seeds prevented germination, but this effect was reversed by ethylene. Tracer studies with 14C-amino acids indicate that ABA does not inhibit total protein synthesis, but it does inhibit emergence in the absence of ethylene. In the presence of ABA plus ethylene, emergence occurred, but no change in total protein synthesis was detected. At 8 weeks after harvest, both germination and incorporation of 2–14C-uracil into RNA were inhibited by ABA and stimulated by ethylene. By 17 weeks after harvest, only the inhibition of germination and its reversal by ethylene were notable. However, at 17 weeks after harvest, ethylene enhanced RNA synthesis when germination and protein synthesis were inhibited by cycloheximide. Development of isocitritase activity in the seeds was inhibited by ABA and the inhibition was reversed by ethylene, indicating that de novo synthesis of protein is inhibited by ABA and activated by ethylene in these seeds. The opposite effects of ABA and ethylene on germination, RNA synthesis and isocitritase activity suggest that germination is controlled at the level of RNA and/or protein synthesis in these seeds. The prevention of germination of dormant seeds in the presence of ethylene by protein- and RNA-synthesis ihhibitors supports this suggestion, but the data do not preclude an action of ABA or ethylene prior to detectable affects on RNA or protein synthesis.


FEBS Letters ◽  
2002 ◽  
Vol 514 (2-3) ◽  
pp. 199-203 ◽  
Author(s):  
Matthew Hiram Taylor ◽  
Matthew Ross Buckwalter ◽  
Amen Craig Stephenson ◽  
Janet Leigh Hart ◽  
Benjamin James Taylor ◽  
...  

2002 ◽  
Vol 76 (15) ◽  
pp. 7578-7586 ◽  
Author(s):  
Bodil Øster ◽  
Per Höllsberg

ABSTRACT Herpesvirus gene expression is divided into immediate-early (IE) or α genes, early (E) or β genes, and late (L) or γ genes on the basis of temporal expression and dependency on other gene products. By using real-time PCR, we have investigated the expression of 35 human herpesvirus 6B (HHV-6B) genes in T cells infected by strain PL-1. Kinetic analysis and dependency on de novo protein synthesis and viral DNA polymerase activity suggest that the HHV-6B genes segregate into six separate kinetic groups. The genes expressed early (groups I and II) and late (groups V and VI) corresponded well with IE and L genes, whereas the intermediate groups III and IV contained E and L genes. Although HHV-6B has characteristics similar to those of other roseoloviruses in its overall gene regulation, we detected three B-variant-specific IE genes. Moreover, genes that were independent of de novo protein synthesis clustered in an area of the viral genome that has the lowest identity to the HHV-6A variant. The organization of IE genes in an area of the genome that differs from that of HHV-6A underscores the distinct differences between HHV-6B and HHV-6A and may provide a basis for further molecular and immunological analyses to elucidate their different biological behaviors.


2004 ◽  
Vol 31 (8) ◽  
pp. 847 ◽  
Author(s):  
Tae-Hwan Kim ◽  
Bok-Rye Lee ◽  
Woo-Jin Jung ◽  
Kil-Yong Kim ◽  
Jean-Christophe Avice ◽  
...  

The kinetics of protein incorporation from newly-absorbed nitrogen (N, de novo protein synthesis) was estimated by 15N tracing in 18-week-old white clover plants (Trifolium repens L. cv. Regal) during 7 d of water-deficit treatment. The physiological relationship between kinetics and accumulation of proline and ammonia in response to the change in leaf-water parameters was also assessed. All leaf-water parameters measured decreased gradually under water deficit. Leaf and root dry mass was not significantly affected during the first 3 d when decreases in leaf-water parameters were substantial. However, metabolic parameters such as total N, proline and ammonia were significantly affected within 1 d of commencement of water-deficit treatment. Water-deficit treatment significantly increased the proline and NH3–NH4+ concentrations in both leaves and roots. There was a marked reduction in the amount of N incorporated into the protein fraction from the newly absorbed N (NANP) in water-deficit stressed plants, particularly in leaf tissue. This reduction in NANP was strongly associated with an increased concentration of NH3–NH4+ in roots (P≤0.05) and proline (P≤0.01) in leaves and roots. These results suggest that proline accumulation may be a sensitive biochemical indicator of plant water status and of the dynamics of de novo protein synthesis in response to stress severity.


Author(s):  
Margarita Elena Papandreou ◽  
Konstantinos Palikaras ◽  
Nektarios Tavernarakis

2002 ◽  
Vol 87 (04) ◽  
pp. 674-683 ◽  
Author(s):  
John Martens ◽  
Lambert Dorssers ◽  
Jan Klijn ◽  
John Foekens ◽  
Anieta Sieuwerts

SummaryIn breast stroma urokinase plasminogen activator (uPA) is predominantly expressed by fibroblasts located in the near vicinity of tumor cells, and fibroblast-derived insulin-like growth factor-1 (IGF-1) may be involved in inhibiting the expression of uPA in these fibroblasts. To investigate a possible role for fibroblast growth factors (FGFs), we evaluated the expression of components of the PA system and the IGF system in normal and tumor-tissue-derived human breast fibroblasts exposed to various FGFs in vitro. mRNA analysis revealed that FGF-1, FGF-2 and FGF-4 induced the mRNA expression levels of uPA, tPA, uPAR, PAI-1 and PAI-2, and reduced those of IGF-1, IGF-1R, IGF-2R and IGFBP-4, without significantly affecting the levels of IGFBP-3, IGFBP-5 and IGFBP-6 mRNA. Concerning the expression of IGF-2 mRNA, the effects mediated by FGF-1, FGF-2 and FGF-4 were divergent. In general, the effects elicited by FGF-1 on the various mRNA levels studied were rapid and short-term. Those mediated by FGF-2 overall lagged behind but were longer-lasting. For FGF-4 an in between pattern was observed. Blocking transcription and translation demonstrated that a) both the FGF-1 and FGF-2 induced effects were the result of altered gene transcription or mRNA stability, b) the short-term effects mediated by FGF-1 and FGF-2 required de novo protein synthesis, and c) the long-term effects elicited by FGF-2 did not depend on de novo protein synthesis during the first 24 h, but were triggered by proteins produced or made available thereafter. The data presented propose that of the FGFs studied (FGF-1, -2, -4, -5, and -7), FGF-2 is the most attractive target for therapeutical strategies aimed at diminishing the contribution of stromal fibroblasts in the PA-directed breast tumor proteolysis.


1981 ◽  
Vol 36 (11-12) ◽  
pp. 942-950 ◽  
Author(s):  
Peter Westhoff ◽  
Kurt Zimmermann ◽  
Frank Boege ◽  
Klaus Zetsche

Abstract Transfer of heterotrophically grown cells of the unicellular green alga Chlorogonium elongatum to autotrophic growth conditions causes a 10 -15 fold increase in the amount of the chloroplastic enzyme ribulose-1,5-bisphosphate carboxylase. This increase was found to be due to de novo synthesis. The relative proportions of large and small subunits of the enzyme do not change. Their ratio is close to 3.4, the proportions in weight of the two subunits in the holoenzyme. Continous labelling with [35S]sulfate reveals that the ratios of incorporation into large and small subunits are essentially the same in autotrophic and heterotrophic cells. Pulse-chase experiments show that the subunits are degraded synchronously. The coordinated subunit synthesis cannot be uncoupled using inhibitors of protein and RNA synthesis or high temperature of cultivation of the alga. The results suggests a very tightly coordinated synthesis of the large and small subunits of ribulosebisphosphate carboxylase.


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