Biosynthetic pathways terpene

Recently it was shown by radiolabeling studies that the formation of the serrulatane skeleton is catalyzed by the pseudopterosin diterpene cyclase, which can be considered as a key enzyme in terpene biosynthetic pathways (Scheme 2). The elisabethatriene cyclase is a monomer with a molecular mass of47kDa [25]. 

The biosynthesis of synthetic natural rubber has been completely determined and appears in Fig. 15.1. Many plants and animals use this same biosynthetic pathway to make hundreds of terpenes and steroids from their common isoprenoid building blocks. 

The thiazole ring is assembled on the 5-carbon backbone of 1-deoxyxylulose 5-phosphate, which is also an intermediate in the alternative biosynthetic pathway for terpenes (Fig. 22-2) and in synthesis of vitamin B6 (Fig. 25-21). In E. coli the sulfur atom of the thiazole comes from cysteine and the nitrogen from tyrosine.374 The same is true for chloroplasts,375 whereas in yeast glycine appears to donate the nitrogen.372 The thiamin biosynthetic operon of E. coli contains six genes,372a 376 one of which (ThiS) encodes a protein that serves as a sulfur carrier from cysteine into the thiazole.374 The C-terminal glycine is converted into a thiocarboxylate ... 

The diverse, widespread and exceedingly numerous class of natural products that are derived from a common biosynthetic pathway based on mevalonate as parent, are synonymously named terpenoids, terpenes or isoprenoids, with the important subgroup of steroids, sometimes singled out as a class in its own right. Monoterpenes, sesquiterpenes, diterpenes and triterpenes are ubiquitous in terrestrial organisms and play an essential role in life, as we know it. Although the study of terrestrial terpenes dates back to the last century, marine terpenes were not discovered until 1955. 

Figure 30-1 Summary of biosynthetic pathways to fatty acids, terpenes, and steroids...

Simpson JS, Brust A, Garson MJ (2004) Biosynthetic Pathways to Dichloroimines Precursor Incorporation Studies on Terpene Metabolites in the Tropical Marine Sponge Stylotella aurantium. Org Biomol Chem 2 949... 

Unlike the biosynthetic route to 2 and 3, the synthetic approaches to these molecules are characterized, instead, by deconstruction of terpene natural products further along the biosynthetic pathway. Preparation of (+)-5-epi-aristolochene (2) has so far only been carried out using a semisynthetic strategy from the natural product 12 [27], which is available from pepper (Capsicum annum) fruits in high quantities [28]. The synthetic route started with O-acetylation of 12 to give... 

The biosynthesis of monoterpenoids and camphor has been described by several authors (108-llU). Ruzicka (115,116) proposed a unified biogenetic scheme for terpenes. The biosynthetic building blocks for these terpenes are iso-prene units. The biosynthetically active isoprene units are isopentenyl pyrophosphate [l] and dimethyl allyl pyrophosphate [2] the compounds that are derived from acetate via mevalonic acid (Scheme V). Geranyl pyrophosphate [3] is the C-10 precursor for the terpenes (117). Banthorpe and Baxendale (ll8) confirmed the biosynthetic pathway of (iamphor via acetate mevalonate by conducting degradation study of camphor, biosynthesized from l c labelled mevalonic acid. The biosynthesis of camphor is summarised in Scheme VI. 

Figure 10.7 All terpenes are derived from allylic diphosphates which are polymers of repeating isopentyl units (IPP) put together by the action of prenyltransferases. In plants, IPP can be derived from the mevalonate biosynthetic pathway (a cytoplasmic pathway) or the methyl erythritol phosphate pathway (a plastidic pathway). Monoterpenes are then derived from the CIO precursor geranyl diphosphate (GPP), sesquiterpenes from the C15 precursor famesyl diphosphate (FPP), and diterpenes from the C20 precursor geranylgeranyl diphosphate (GGPP) by the action of terpene synthases or cyclases, which divert carbon into the specific branch pathways.

Extractives are formed through a variety of biosynthetic pathways illustrated for terpenes in Fig. 5-1. 

Similar to other natural products, phytotoxins are classified on the basis of their structural types considering their biosynthetic pathways. Among various phytotoxin families, polyketides including aromatic and reduced polyketides, peptides including diketopiperazines, and terpenes are most frequently described in the literature. In this section, representative phytotoxins that are well-characterized biosynthetically and physiologically will be introduced. 

Poulter, C.D., and Rilhng, H.C. (1978). The prenyl transfer reaction. Enzymatic and mechanistic studies of the l -4 coupling reaction in the terpene biosynthetic pathway. Acc Chem Res 11 307-313. 

Sites of biosynthesis are compartmentalized in the plant cell. While most biosynthetic pathways proceed (as least partially) in the cytoplasm, there is evidence that some alkaloids (such as coniine, quinolizidines and caffeine), furanocoumarins and some terpenes (such as monoterpenes, diterpenes. 

Sillen LG (1967) How have seawater and air got their present compositions Chem Br 1 291-297 Simpson JS, Garson MJ (2004) Biosynthetic pathways to isocyanides and isothiocyanates precursor incorporation studies on terpene metabohtes in the tropical marine sponges Amphimedon terpenensis and Axinyssa n.sp. J Org Biomol Chem 2 939-948... 

E)-l-Hydroxy-2-methyl-but-2-ary 1-4-diphosphate (44) has been prepared in six steps from tetrahydropyranyl ether (42), derived from hydroxyacetone and phosphonium ylide (43), in 35% yield. The compound (44) was shown to be identical with the product of I spG protein, which serves as an intermediate in the non mevalonate terpene biosynthetic pathway (Scheme 7). ... 

Even though E. coli is a very well-studied bacterium, many interesting mechanistic problems in cofactor biosynthesis in this organism remain unsolved. The mechanisms for the formation of the nicotinamide ring of NAD, the pyridine ring of pyridoxal, the pterin system of molybdopterin, and the thiazole and pyrimidine rings of thiamin are unknown. The sulfur transfer chemistry involved in the biosynthesis of lipoic acid, biotin, thiamin and molybdopterin is not yet understood. The formation of the isopentenylpyrophosphate precursor to the prenyl side chain of ubiquinone and menaquinone does not occur by the mevalonate pathway. None of the enzymes involved in this alternative terpene biosynthetic pathway have been characterized. The aim of this review is to focus attention on these unsolved mechanistic problems. 

The biosynthesis of menaquinone is outlined in Fig. 44. Isomerization of chorismate to isochorismate followed by condensation with a-ketogluta-rate and aromatization gives o-succinylbenzoic acid. Conversion of 238 to the CoA thio ester, followed by cyclization, prenylation and methylation completes the biosynthesis. The biosynthesis of the prenyl side chain follows the alternative terpene biosynthetic pathway described for ubiquinone. 

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