Mechanisms of Synthesis of Waxy Esters in Broccoli (Brassica oleracea) *

1968

Plant Physiol.

Self Cite

Abstract. In isolated tobacco leaves L-valine-U-14C gave rise to labeled even-numbered isobranched fatbty acids containing 16 to 26 carbon atoms and iso C29, iso C31, and iso C3, paraffins. L-Isoleucine-U-14C on the other hand produced labeled odd-numbered anteiso C17 to C97 fatty acids and anteiso C30 and C32 paraffins. Trichloroace'tic acid inhibited the incorporation of isobutyrate into C90 and higher fatty acids and paraffins without affecting the synthesis of the Cl. and C,, fatty acids. Thus the very long branched fatty acids are biosynthetically related to the paraffins. In Senecio odoris leaves acetate-1_14C was incorporated into the paraffins (mainly n-C,1 ) only in the epidermis although acetate was readily incorporated into fatty acids in the mesophyll tissue. Similarly only the epidermal tissue incorporated acetate into fatty acids longer than C18 suggesting that the epidermis is the site of synthesis of both paraffins and the very long fatty acids. In broccoli leaves n-C., acid labeled with 14C in the carboxyl carbon and 3H in the methylene carbons was incorporated into C, paraffin without the loss of 14C relative to 3H. Since n-C18 acid is known to be incorporated into the paraffin without loss of carboxyl carbon these results suggest that the condensation of C32 acid with CV, acid is not responsible for n-C29 paraffin synthesis in this tissue. Thus all the experimental evidence thus far obtained strongly suggests that elongation of fatty acids followed by decarboxylation is the most likely pathway for paraffin biosynthesis in leaves.The epidermis of plants is covered with a thin l.ayer of waxy !chemicals. The chemistry of this suirface wax 'ha.s been reviewed thoroughily in the past few years (2, 3, 4). The 2 most common componen-ts of the surface wax are waxy esters and hydrocarbons. The waxy esters are synithesized in the leaf by the 'esteri.ficaition of aliphatic prima.ry alcohols with fatty acyl moieties from fatty acyl coenzvme A, pho-spholliipid, o,r free fatty acid (12).The stra,ight chain 'hydrocarbons in planits originate from acetate (9). Longer fatty acicds suich as C, ,, and C,8 are inco,riporated into the nt-C..9 hydrocarbon of Brassica oleracea more efficientlv and wiithoutt prio,r degradation of their carboni chains (10). TII thi.s tissule C,, and C,8 fatty acidls are also incorporaited inito very long fatty ac,ids (C.,,)-C.,,). The effects o,f light, 3-(4-,chl'orophenl)l)-1,1-climethyl uirea (CMU), and trichilo,roacetate oni the incorporation of laibeled prectirsors 'into paraffins and 'very long fatty acid's ssuggested thait ni-paraffins are synthesized by elongation of a common fattv acid (C1,,,) followed by decarboxylaition as shown in Scheme I (11). Althouigh this hypothesis was derived from work on the biosyntbhesis of it-C.,9 paraffin in B. oleraceo, it seemed likely that stuch a hypoithesis would be of wider application. In order to tesft suich a poss bility Sencecio odoris, a plant whiich has priniarily it-C: l paraffin and tobacco wihich has considerabl'e prolport:onis of ...

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Further Evidence for an Elongation-Decarboxylation Mechanism in the Biosynthesis of Paraffins in Leaves

1968

Plant Physiol.

Self Cite

“…Leaves of different age groups were collected and 12-mm diameter discs were cut from each. After the discs were washed thoroughly with water, 20 discs of each age group were placed at the bottom of 125-ml Erlenmeyer flasks with 0.5 ml of palmitic acid-1-"4C (55 mc/mmole) solution containing 7.5 X 106 cpm (70% efficiency) and prepared as described before (5). The discs were incubated in the radioactive solution for 3 hr at 30 C in a gyratory water bath shaker.…”

mentioning

confidence: 99%

Cutin Biosynthesis in Vicia faba Leaves

1970

Plant Physiol.

Self Cite

Plant cuticle consists of a polymer of hydroxy fatty acids called cutin, which is embedded in wax. Although in recent years the chemistry and biosynthesis of the wax components have been studied to a certain extent (1,6), cutin biosynthesis remains merely speculative. Some information on the structure of hydroxy fatty acids that make up the cuticle is available (2, 3). Recently a tracer method coupled to a novel method of cleavage of the polymer was developed to study the biosynthesis of this polymer (7). These techniques can be used to determine at what stage of leaf growth cutin biosynthesis occurs. The results described in this communication clearly demonstrate that the most rapidly expanding leaves of Vicia faba synthesize cutin most rapidly, and that cutin synthesis virtually stops when the leaf reaches full expansion.V. faba plants grown at 22 C with a 16-hr day in a soil-sand mixture (2: 1) were used in all experiments. Three-week-old plants with five or six leaves were selected in such a way that all top leaves were of about equal age, and the lower leaves of the different plants had comparable ages. Leaves of different age groups were collected and 12-mm diameter discs were cut from each. After the discs were washed thoroughly with water, 20 discs of each age group were placed at the bottom of 125-ml Erlenmeyer flasks with 0.5 ml of palmitic acid-1-"4C (55 mc/mmole) solution containing 7.5 X 106 cpm (70% efficiency) and prepared as described before (5). The discs were incubated in the radioactive solution for 3 hr at 30 C in a gyratory water bath shaker.At the end of the incubation period the leaf discs were washed twice, each time with 50 ml of distilled water. The discs were then homogenized (Ten-Broeck) in water and centrifuged at 15,000g for 15 min. The residue was treated with 25 ml of a 2:1 mixture of chloroform and methanol for 15 min and then centrifuged at 15,000g for 15 min. This treatment was repeated four more times and the final residue was similarly treated twice with 25 ml each of tetrahydrofuran. Little '4C was released into the solvent at this stage. The radioactivity remaining in the residue has been demonstrated to be primarily in cutin (7). This insoluble material was refluxed with LiAlH4 in tetrahydrofuran (previously treated with solid KOH and then distilled over LiAIH4) for 24 hr. The excess LiA1H4 was decomposed by a careful addition of the reaction mixture into water. Dilute HCI was added and the lipids were extracted five times with ethyl ether, and the ether was evaporated under reduced pressure. The residue was dissolved in 0.3 ml of a 2:1 mixture of chloroform and methanol and 10

“…With plant enzymes it was demonstrated for the first time that fatty acyl-CoA is used to esterify fatty alcohol (Kolattukudy 1967) (Fig. 11.6).…”

Section: Esterificationmentioning

confidence: 99%

Wax Esters: Chemistry and Biosynthesis

2014

Lipids and Skin Health

Wax esters are unique surface lipids found on the surface of terrestrial organisms. After a brief review of the composition, the mechanisms used in their biosynthesis by sebaceous glands are summarized. The molecular biology of biosynthesis of methyl-branched, short chain and very long chain acids, and the biochemical mechanism of the loss of the carboxyl carbon of the elongated very long chain acids to generate alkanes are reviewed. The molecular biology of biosynthesis of the major types of molecules contains the hydroxyl group(s) to which the acids are esterified and the molecular biology of the esterification process are reviewed. The molecular bases of seasonal and hormonal regulation of biosynthesis of wax esters that implicate some functions of the wax esters are reviewed. Core Messages• Wax esters are unique surface lipids found on the surface of terrestrial organisms.• These unusual lipids that coat the surface of animals offer unique biochemical challenges that are associated with skin health issues.