14C Acetate incorporation

Rafaeli A. and Soroker V. (1989) Cyclic AMP mediation of the hormonal stimulation of 14C-acetate incorporation by Heliothis armigera pheromone glands in vitro. Mol. Cel. Endocrinol. 65, 43-48. 

Soroker V. and Rafaeli A. (1989) In vitro hormonal stimulation of [14C]acetate incorporation by Heliothis armigera pheromone glands. Insect Biochem. 19, 1-5. 

Sethoxydim (IpM) inhibited the biosynthesis of fatty acids in isolated oat chloroplasts (measured via [14C]acetate incorporation into the total fatty acid fraction) to ca. 60 %, whereas in the isolated chloroplasts of the dicotyledonous pea plants their synthesis was not affected by sethoxydim. About 50 % inhibition of fatty acid synthesis by IpM sethoxydim was detected in experiments with chloroplasts isolated from Poa pratensis, a herbicide-sensitive grass. In chloroplasts isolated from Poa annua, which as a whole plant is tolerant against sethoxydim [7], fatty acid biosynthesis was also blocked (to ca. 45 %) by IpM sethoxydim (Fig. 2). This indicates a basic difference in the mechanism of tolerance for Pisum sativum and Poa annua, respectively. In Poa annua, the tolerance is apparently based on... 

Fig.2 [2-14C]acetate incorporation into the total fatty acid fraction of chloroplasts isolated from different sensitive and tolerant plants in addition of IpM sethoxydim. The incorporation rates of the controls in nmol acetate (mg chlorophyll h)" were 32 for Avena sativa, 38 for Pisum sativum, 4 for Poa pratensis and 6 for Poa annua. Mean values of 4 determinations with SD. 

Initially, attempts to grow the organism on sodium acetate as the sole source of carbon were unsuccessful, but the difficulties were overcome and mannitol, arabinitol, erythritol, glycerol, maltose, and a,a-trehalose were produced. This was a useful development because conditions were established for the incorporation of [14C] acetate, thereby making labeled polyols and disaccharides available. 

Bloch therefore suggested isoprene units could be condensed first to give squalene and then cholesterol, an extension of Ruzicka s isoprene rule for the biosynthesis of linear and cyclic terpenoids. It was then necessary to show that selectively labeled 14C-acetate could get incorporated into squalene with the correct distribution of 14C and that this squalene could give rise to cholesterol, also with the appropriate position of the 14C label. 

The red algal chamigrene sesquiterpene elatol (Structure 2.78) has been shown to deter feeding by reef fishes.93 Specimens of Laurencia elata from Southern Australia show a pronounced seasonal variation in elatol production. Incorporation studies using 14C acetate failed to confirm an acetate-mevalonate path for elatol production.125... 

Garson, M. J., Biosynthesis of the novel diterpene isonitrile diisocyanoadociane by a marine sponge of the Amphimedon genus incorporation studies with [14C]cyanide and sodium [2-14C]acetate, J. Chem. Soc. Chem. Commun., 35, 1986. 

Jones I. F. and Berger R. S. (1978) Incorporation of [1-14C]acetate into cis-7-dodecenyl acetate, a sex pheromone in the cabbage looper Trichoplusia ni. Environ. Entomol. 7, 666-669. 

Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, which had been previously treated with juvenile hormone III (JH III, 2.2 pg/beetle in acetone) and then placed in an aeration tube for 25 to 30 h. Ips paraconfusus and I. pini were each injected with 0.2 pCi of sodium [1-14C]acetate prior to placement in cut pine logs and volatile collection, while D. jeffreyi were each injected with 3.8 (male) and 3.7 (female) pCi of sodium [1-14C]acetate 6.4 (male) and 10.7 (female) h after JH application. (G) The role of the mevalonate pathway in frontalin biosynthesis is supported by the incorporation of radiolabel from [2-14C]mevalonolactone into frontalin by male D. jeffreyi (2.2 pg JH 11 l/beetle in acetone, 10 h incubation and volatile collection, 1.1 pCi of [2 14C] mevalonolactone injected, 20 h volatile collection). Figures adapted from Seybold et al. (1995b) and Barkawi (2002). 

To date, only two other sets of inquilines have been directly examined for their ability to biosynthesize suites of cuticular hydrocarbons that mimic that of their hosts. Larvae of the syrphid fly Microdon albicomatus are obligate predators of the ant Myrmica incompleta, and have qualitatively identical hydrocarbons as host pupae (but different relative abundances). As with the beetles above, [l-14C]acetate was directly incorporated into the fly cuticular hydrocarbons in the same proportions as the various classes of hydrocarbons present (Howard et al., 1990). The other study was by Akino et al. (1999) and involved the larvae... 

Most of the work on the biosynthesis of Lythraceae alkaloids has been done by Spenser et al. (10, 84-87). First, the validity of the pelletierine hypothesis (c) of Ferris et al. (62) has been tested. The pelletierine (126) nucleus is generated from L-lysine (181) via cadaverine (182), and presumably A -piperideine (132) and its side chain originate from the acetate. Incorporation of radioactivity from 14C-labeled samples of these precursors to decodine (6) and decinine (2) in Decodon verticilatus has been investigated (85, 87). 

A number of studies with widely diverse species have established that the major site of cuticular hydrocarbon synthesis is within the cells associated with the epidermal layer or the peripheral fat body, particularly the oenocytes. In Schistocerca gregaria, Diehl (1973, 1975) separated the oenocyte-rich peripheral fat body from the central fat body tissue and observed the highest rate of hydrocarbon synthesis in the oenocyte-rich peripheral fat body. In Tenebrio molitor, Romer (1980) demonstrated that isolated oenocytes efficiently and specifically incorporated [14C]acetate into hydrocarbon. Similar studies in Periplaneta americana (Nelson, 1969), Sarcophaga bullata (Arnold and Regnier, 1975), and Musca domestica (Dillwith et al., 1981) demonstrated that hydrocarbon synthesis occurs primarily in the epidermal tissue. 

Dioscorine.—Labelling of C-5, C-.10, and C-12 of dioscorine (2) by [l-14C]acetic acid8 indicates that C-5, C-6, C-9, C-10, C-ll, C-12, and C-13 derive from acetate. This leaves a cyclic C5N unit unaccounted for, which, from the wealth of evidence on the biosynthesis of similar systems (see previous Reports), one expects will arise from the amino-acid lysine via A piperideine (1), an expectation not realized since neither compound is satisfactorily incorporated into dioscorine (2).8... 

Shihunine.—Preliminary results139 indicated that the orchid alkaloid shihunine (153) was derived from (152), an important intermediate in naphthoquinone biosynthesis.140 Further details are now available in a full paper.141 The intact incorporation of (152) is affirmed by the observation that (152), labelled with 13C at C-l, was an efficient and specific precursor for (153). [l-14C]Acetate was examined as a shihunine precursor and was found only to label C-5. This is consistent with the expected formation of (152) from shikimic acid (144) and a-ketoglutarate (151),140 the latter gaining acetate label in its carboxy-groups through the tricarboxylic acid cycle. 

We decided to focus our attention on de novo fatty acid biosynthesis based upon our observations and those reported in the literature (12). To determine whether fatty acid biosynthesis was inhibited, we determined the effect of the herbicides on incorporation into palmitic (16 0) acid, the first product of fatty acid biosynthesis. Maize leaf discs were incubated for 40 min in 14C -acetate, after which fatty acids were extracted. As shown in Table II, both tralkoxydim and haloxyfop significantly reduced the amount of acetate incorporated into palmitic acid. Thus, these compounds affected a step early in lipid biosynthesis. 

C]Cholesterol was readily converted into 19-nor-sterols by the sponge Axinella polypoides, but very little de novo synthesis of these sterols from [1-14C]acetate occurred.354 Similarly, whilst [4-14C]cholesterol was incorporated into 3/3-hydroxymethyl-A-nor-5a-steranes by A. verrucosa, no incorporation of tracer from [l-14C]acetate could be demonstrated.355 These results suggest that the unusual nor-sterols in sponge species might arise by modification of dietary sterols. Ring contraction in cholesterol to yield the A-nor-steranes does not result in the elimination of C-4 of the substrate, nor does this carbon form the 3/3-hydroxymethyl group of the product. 

The incorporation of [2-14C]pyruvate and [l-14C]acetate into sugars 17 and 18 was investigated.27 Oxidation of the methyl glycosides of sugar 17 with periodate yielded acetaldehyde from the 1-hydroxyethyl branch. The acetaldehyde (2,4-dinitrophenyl)hydrazone was further oxidized by Kuhn-Roth oxidation to acetic acid, which was degraded by the Schmidt reaction to methylamine and carbon dioxide. Periodate oxidation of the methyl glycosides of sugar 18 produced acetic acid from the C-acetyl branch. The acetic acid was isolated, and purified as 1-acetamidonaphthalene. 

After 1 h of reperfusion following 2 or 3 h of MCAO in conscious rats, regional as well as cellular differences were found with regard to incorporation of 14C into glutamate and glutamine from [14C]glucose or [14C]acetate (Thoren et al., 2005,... 

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