Growth-associated synthesis

Keywords. Poly(3-hydroxybutyrate), Metabolic sequences, Fine regulation, Poly(3HB) cycle, Strategic survival polymer, Growth-associated synthesis, Energy-generating and -consuming synthesis, Optimization... 

The growth-associated synthesis of poly(3HB) is clearly of selective advantage. The synthesis of poly(3HB) is not only - as stated above - an investment in the future, but also an opportunity to cope with and widen actually existing intrinsic bottlenecks. 

If poly(3HB) formation is an effective strategy for survival the poly(3HB) machinery should be ready for use at all times. Its utilization (and the extent to which it is expressed) is determined by external conditions, the metabolic and regulatory disposition of a given strain, and the substrate offered. From this perspective, growth-associated synthesis of poly(3HB) (or, more precisely, poly(3HB) formation-associated growth) ought to occur more frequently than has yet been observed and reported. 

Profile for growth and product synthesis according to different production models (A) growth associated production B) growth partially associated production, and C) non-growth associated production. 

While axonal transport and protein synthesis are essential for nerve regeneration (see review by Grafstein and Forman, 1980), the overall rate of fast transport is not affected by sciatic axotomy (Griffin et al., 1976 Bisby, 1978 Crescitelli et al., 1989). Despite this, there is an increase in the amount of small proteins and polypeptides, known as growth-associated-peptides (GAPs), destined to be incorporated in the regrowing plasma membrane and cy-toskeleton (Skene and Willard, 1981 Bisby, 1988). One of these GAPs is B-50, also known as GAP-43, which is discussed in Section 2.4. 

Specific growth rate of the producing strain is also a relevant parameter for enzyme production by fermentation. Many enzymes are synthesized as growth-associated metabolites so that cell specific growth rate has a direct impact on enzyme specific rate of synthesis as shown by the non-structured model of Luedeking and Piret (1959) ... 

HydrophobicaHy Modified, Ethoxylated Urethane. HEUR associative thickeners are in effect poly(oxyethylene) polymers that contain terminal hydrophobe units (66). They can be synthesized via esterification with monoacids, tosylation reactions, or direct reaction with monoisocyanates. There are problems associated with aH of the methods of synthesis. The general commercial procedure for their synthesis is by a step-growth addition of... 

Product formation kinetics in mammalian cells has been studied extensively for hybridomas. Most monoclonal antibodies are produced at an enhanced rate during the Gq phase of the cell cycle (8—10). A model for antibody production based on this cell cycle dependence and traditional Monod kinetics for cell growth has been proposed (11). However, it is not clear if this cell cycle dependence carries over to recombinant CHO cells. In fact it has been reported that dihydrofolate reductase, the gene for which is co-amplified with the gene for the recombinant protein in CHO cells, synthesis is associated with the S phase of the cell cycle (12). Hence it is possible that the product formation kinetics in recombinant CHO cells is different from that of hybridomas. 

ET-1 also stimulates anti-apoptotic signal cascades in fibroblasts, vascular smooth muscles and endothelial cells (via phosphatidylinositol-3-kinase and Akt/pro-tein kinase B). In prostate and ovarian cancer, upregulation of endothelin synthesis and ETA receptors has been associated with a progression of the disease. The inhibiton of ETA receptors results in a reduced tumour growth. In malignant melanoma, ETB receptors are associated with tumour progression. Endothelins can also stimulate apoptosis in stretch-activated vessels via the ETB receptor, which contrasts the above-mentioned effects. The molecular basis for these differential anti- and pro-apoptotic reactions mediated by endothelins remains elusive. 

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