Propionate, labelled

The complex pathway for the anaerobic degradation of propionate by Smithella propionica and Methanospirillum hungatei involves reaction of two molecules of propionate followed by rearrangement to 3-ketohexanoate. The details were elucidated using C-propionate labeled at Cj, C2, C3, or at both Cj and C3 (de Bok et al. 2001). 

When the sacoglossan Placobranchus ocellatus was immersed in seawater containing 14C sodium hydrogen carbonate, 14C label was incorporated into both 9,10-deoxytridachione (Structure 2.124) and the photorearrangement product photodeoxytridachione (Structure 2.125).242 In Elysia viridis, sodium [l-14C]propionate was incorporated into elysione (Structure 2.126), an ichthyotoxic metabolite found in the mollusc s mucus secretions.237 Attempts to repeat this propionate labeling experiment in Elysia timida and to test the putative role of acetate in the biosynthesis of 15-norphotodeoxytridachione (Structure 2.127) were unsuccessful.237 243 The metabolites shown in Structures 2.124, 2.125, 2.126, and 2.128, some of which were toxic, were present in the mucus secretion of Elysia timida, consistent with a defensive role.243 The hypothesis that these complex pyrones function as suncreens242 has been disputed.243... 

Methyl-branched fatty acids are intermediates in branched alkane biosynthesis (Juarez et al., 1992). Thus, [l-14C]propionate labeled methyl-branched fatty acids of 16-20 carbons, but did not label straight chain-saturated and monounsaturated fatty acids (Chase et al., 1990). 

It is well established that propionate can be utilized for the methyl branch unit in methyl branched hydrocarbons in insects (4-7), and recent data have shown that the methyl branches are inserted early during chajij elongation rather than toward the end of the process (13,16). C-NMR analysis demonstrated that propionates labeled with C in either the 1, 2 or 3 positions are incorporated into the methyl branched alkanes of insect cuticular lipids. C-3 of propionate becomes the branching methyl carbon, C-2 becomes the tertiary carbon and C-l the carbon adjacent to the tertiary carbon (13,16,17) in these methyl branched hydrocarbons. 

These results could be explained if, as was suggested by the data of Dillwith et al. (14). there is a pathway In which propionate is directly converted to acetate with the loss of carbon 1 and the oxidation of carbon 3. With a pathway of this type, propionate labeled in carbon 1 would lose its label if it were converted to acetate prior to incorporation into other compounds. However, if propionate were labeled in carbon 2 or carbon 3 it would retain its label upon conversion to acetate. Therefore, any label incorporated into JH or hydrocarbon from propionate labeled in carbon 1 would have to be the result of propionate being utilized as an intact unit. Incorporated label from propionate labeled in carbon 2 or carbon 3 could result from direct Incorporation of propionate or from conversion of propionate to acetate prior to being utilized for JH or hydrocarbon biosynthesis. Thus, the labeling patterns seen by Schooley, ejt al. (O and Dillwith, et a l. (14) could be the result of the retention of label from carbon 2 or carbon 3 of propionate, and the loss of label from carbon 1 of propionate during the conversion of propionate to acetate. 

Tracer studies have confirmed the kind of bond cleavage indic ited by the stereochemical evidence. When ethyl propionate labeled with was hydrolyzed by base in ordinary water, the ethanol produced was found to be enriched in the propionic acid contained only the ordinary amount of... 

U- C]phenylalanine, and [4- C]erythrose hardly at all. [Carboxy- C]-propionate, [methylene- C]ma onaXe, and [m //7jr/- C]methionine were then administered and the carbons labeled were identified, employing the carbon assignments made previously (see Table 5), in the cmr spectra of the labeled streptovaricin D (the most abundant streptovaricin found in the biosynthetic studies). Results showed that [f /r/70A 3 - C]propionate labels eight carbon atoms to approximately the same extent, C-1, C-5, C-7, C-9, C-11, C-13, C-15 and C-19, thus establishing the amide-head direction of biosynthesis (Scheme a) (90). By implication, carbons C-2, C-6, C-8, C-10, C-12, C-14, C-16, and C-20, plus the 2-, 6-, 8-, 10-, 12-, 14-, 16- and 20-methyl carbons were also derived from propionate. Sodium [2- C]malonate labeled equally C-4 and C-18 (by implication, carbons C-3 and C-17 were also derived from malonate), which further... 

Carbon magnetic resonance spectroscopy was used to demonstrate that sodium [carZ uxy- C] propionate labeled C-1, C-7, C-9, and C-13 (and, by implication, that C-2, C-8, C-10, C-14 and the 2-, 8-, 10- and 14-methyl carbons were also derived from propionate), and that [me//zy/- C]methionine was the source of the three methoxyl groups (42, 46), This confirmed the amide-head path of biosynthesis (Fig. 35). 

Since ivermectin (= 22,23-dihydroavermectin B ) is obtained by catalytic reduction of avermectin B, the same procedure using tritium gas convenientiy affords tritiated ivermectin (22,23- [JT]-22,23-dihydroavermectin B ). The preparation of a tritiated derivative containing a 22,23-double bond starts with the readily available 5-ketone, which is reduced with [JT]-sodium borohydride stereospecificaHy to a 5- [JT]-derivative (40). Carbon-14 labeled avermectins can be obtained by a biosynthetic process using sodium (l- C)propionate as labeled precursor (48). 

This reaction provides a wide variety of products since decomposition of the deuterated alkylborane intermediate (164) can be achieved with hydrogen peroxide to yield labeled alcohols (165), with hydroxylamine-O-sulfonic acid leading to deuterated amines (166), as well as with boiling propionic acid or propionic acid-OD, to form mono- (167) or dideuterio (168) hydrocarbons, respectively. Furthermore, if a monodeuterium label at the sterically more accessible position (170) is sufficient, the use of expensive metal deute-... 

The successful labeling of the elusive 14a-position in cholestane represents a very important application of this reaction.It is known that hydroboration of the double bond in 5of-cholest-14-ene (174) occurs on the a-side. Consequently, by using deuteriodiborane (generated by the reaction of boron trifluoride etherate with lithium aluminum deuteride) and then propionic acid for hydrolysis of the alkylborane intermediate, 14a-d,-5a-cholestane (175) is obtained in 90% isotopic purity. This method also provides a facile route to the C-15 labeled analog (176) when the alkylborane derived from 5a-cholest-14-ene is hydrolyzed with propionic acid-OD. ... 

The biosynthesis of Me3,Mel 1-29 H takes place in oenocyte cells, released into the hemolymph and transported by lipophorin to peripheral tissues (Fig. 7) [71, 231, 232]. Direct evidence for oenocytes biosynthesizing hydrocarbon has come recently with the dissociation of oenocytes from epidermal cells and in vitro incubation with labeled propionate [233]. Differential uptake of some hydrocarbons in different tissues has also been documented although the exact mechanism behind the differential placement of hydrocarbons is unknown [20,128,230,232,234]. Although the biosynthesis of hydrocarbons may not be under direct endocrine regulation supply of precursor hydrocarbon that is converted to the sex pheromone is a requirement. 

The study above does not account for the extra six carbons acquired in the conversion of piperideine (8, 10 carbons) to phlegmarine (9, 16 carbons). It was initially proposed that the carbons were incorporated via pelletierine (12), which was incorporated twice into lycopodine resulting in two symmetrical halves of the alkaloid (Scheme 6.2). However, when 14C-labeled pelletierine (12, label at C2) was fed to the plant, degradation studies of lycopodine revealed that only one half consisted of the 14C label from pelletierine (the half containing C9-C16) [10]. The other half does not result from pelletierine 12 but must be something similar in structure since it does contain the piperideine unit (8) resulting from lysine. It was of interest then to determine the exact source of the three-carbon propionate unit in pelletierine (12). 

Conjugates of (strept)avidin with these fluorescent probes may be prepared by activation of the phycobiliprotein with N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) to create a sulf-hydryl-reactive derivative, followed by modification of (strept)avidin with 2-iminothiolane or SATA (Chapter 1, Section 4.1) to create the free sulfhydryl groups necessary for conjugation. The protocol for SATA modification of (strept)avidin can be found in Section 3.1, this chapter. The procedure for SPDP activation of phycobiliproteins can be found in Chapter 9, Section 7. Reacting the SPDP-activated phycobiliprotein with thiol-labeled (strept)avidin at a molar ratio of 2 1 will result in highly fluorescent biotin binding probes. 

Mesobilirubin-XIIIa labelled with 13C in two propionic acid 13COOH groups, 90, has been synthesized75 in 11% overall yield from K13CN in 10 steps shown in equation 34. 90, a model compound not found in nature, is to be used to study the conformation of bilirubin in solution76 or when bound to proteins or in membranes to understand its ability to cross several selective physiological barriers such as placenta and blood-brain barrier... 

The immunosuppressant compound170 FK-506, similar in effect to cyclosporin A, the leading drug for use in immune system suppression to prevent rejection of transplanted organs171, has been labelled at carbon atoms 10, 16, 18, 21a, 24 and 26 by fermentative biosynthesis using sodium [l-14C]propionate as a precursor172. The same 13C-labelled positions were derived from [l-13C]propionate. FK-506 producing culture Streptomyces tsukubaenis no 9993 has been utilized in this biosynthesis (120 h incubation at 29 °C). 

A polyketide/fatty acid-type metabolic route using three propionate units has been shown by stable isotope-labeled probes and MS to the biosynthetic route towards the production of the insect pheromone (Sl-d-methyl-d-heptanone in the ant Harpegnathos saltator. 

Thus, it is difficult to assign contributions of any protonated heme propionates without/urther distinction such as C-labeling. (From Mileni et ah, 2005)... 

Mileni, M. Haas, A. H. Mantele, W. Simon, J. Lancaster, C. R. D. Probing Heme Propionate Involvement in Transmembrane Proton Transfer Coupled to Electron Transfer in Dihemic QuinokEumarate Reductase by C-Labeling and FTIR Difference Spectroscopy. Biochemistry 2003, 44, 16718-16728. 

Slepnev et al. [313] presented a simple method for protein radio-labeling with Bolten-Hunter reagent (iV-hydroxy succinimide ester of 3-(p-hydroxy di-iodophenyl)) propionic acid) in AOT/octane-RMs using mouse IgG, human transferrin, protein A, and a2-interferon as labeling examples. The yield of radio-labeling in RMs was found to be higher than that achieved in homogeneous aqueous solution. 

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