Poly biosynthetic pathway

In contrast to vitamin K, there has been considerably more activity on fermentative approaches to vitamin (50). The biosynthetic pathway to vitamin K2 is analogous to that of vitamin except that poly(prenylpyrophosphates) are the reactive alkylating agent (51,52). Menaquinones of varying chain lengths from to have been isolated from bacteria. The most common forms are vitamin K2 35, (40) (45) significant amount of K2 20)... 

It has, thus, been demonstrated that redirecting the poly(3HB) biosynthetic pathway from the cytoplasm to the plastid resulted in an approximate 100-fold increase in poly(3HB) production [24]. However, it must be kept in mind that the rate of poly(3HB) biosynthesis in A thaliana leaves was relatively low, since poly(3HB) accumulated progressively over 40-60 days to reach 10-14% of the dry weight, whereas synthesis of starch can reach 17% dry weight for a 12 h photoperiod and seed storage lipids can reach 8% dry weight per day. 

Modulation of the quantity and/or quality of poly(3HAMCL) synthesized in peroxisomes was also achieved by modifying the endogenous fatty acid biosynthetic pathway [58]. For example, expression of the peroxisomal PHA synthase in an A. thaliana mutant deficient in the synthesis of triunsaturated fatty acids [59] resulted in the synthesis of a PHA having an almost complete absence of triunsaturated 3-hydroxyacid monomers [58]. In a different strategy, expression of a fatty acyl-ACP thio esterase in the plastid was combined with the expression of a peroxisomal PHA synthase [58]. Fatty acyl-ACP thioesterases are... 

A novel perspective on the use of the synthesis of PHA in plants was achieved by the expression of the poly(3HB) biosynthetic pathway in the cytoplasm of... 

Poly(3HB) synthesis in various subcellular compartments could be used to study how plants adjust their metabolism and gene expression to accommodate the production of a new sink, and how carbon flux through one pathway can affect carbon flux through another. For example, one could study how modifying the flux of carbon to starch or lipid biosynthesis in the plastid affects the flux of carbon to acetyl-CoA and poly(3HB). Alternatively, one could study how plants adjust the activity of genes and proteins involved in isoprenoid and flavonoid biosynthesis to the creation of the poly(3HB) biosynthetic pathway in the cytoplasm, since these three pathways compete for the same building block, i. e., acetyl-CoA. 

Exposure of various cells to ROIs (H2O2, OC1-) in vitro causes a multitude of biochemical alterations including (a) loss of intracellular ATP and NAD+, (b) stimulation of HMP shunt activity, (c) DNA strand breakage, (d) increase in oxidized protein thiol groups, (e) increase in intracellular Ca2+, (f) activation of poly(ADP-ribose) polymerase, (g) alterations in cell morphology, (h) inhibition of many biosynthetic pathways, (i) 51Cr release, (j) intracellular enzyme... 

Thus from an analysis of the biosynthetic gene clusters as well as from earlier biosynthetic studies (often with blocked mutants), it is useful to divide the poly-ketide biosynthetic pathway into PKS reactions and post-PKS tailoring steps. Several of the latter were investigated with respect to biosyntheses of angucy-clin(on)es and natural products derived thereof. Intensive studies of various blocked mutant products of Streptomyces fradiae Til 2717 resulted in a well established sequence of the late steps of urdamycin A (281) biosynthesis (Scheme 63) [164]. 

Fig. ( 8). Acetate biosynthetic pathway leading to fatty acids and polyketides. Structures of Lepidopteran se.x pheromones can be explained as being derived from poly-p-keto chains, formed by coupling of acetic acid (C2) units via condensation reactions. Adapted from ret [287]...

Slater S, Voige WH, Dermis DE (1988) Cloning and expression in Escherichia coli of the Alcaligenes eutrophus H16 poly-P-hydroxybutyrate biosynthetic pathway. J Bacteriol... 

Proteins are composed of amino acids linked by peptide bonds. Two main biosynthetic pathways for protein production have been identified so far the ribosomal and the non-ribosomal-multi-enzyme paths. The proteins are mainly heteropolymers composed by a variety of amino acids however, three poly(amino acid)s can be obtained through the multi-enzyme pathway cyanophycin (aspartic acid-arginine dipeptide), s-poly-L-lysine and poly-a,p-aspartic acid (Figure 1.5). 

The poly(3HB) biosynthetic pathway has also been successfully expressed in the leucoplasts of developing seeds of B. napus. In these experiments, the phaA, phaB, and phaC genes modified for plastid targeting were expressed imder the control of the Lesquerella fatty acid hydroxylase seed specific promoter. Plants... 

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