Fructose 2,6‐bisphosphate and the climacteric in bananas

Abstract

This work was done to test the view that there is a marked rise in the content of fructose 2,6-bisphosphate during the climacteric of the fruit of banana (Musa cavendishii Lamb ex. Paxton). Bananas were ripened in the dark in a continuous stream of air in the absence of exogenous ethylene. C 0 2 production and the contents of fructose 2,6-bisphosphate and sucrose were monitored over a 15-day period. A range of extraction procedures for fructose 2,6-bisphosphate were compared. Recovery of fructose 2,6-bisphosphate added to samples of unripe fruit varied from poor to unmeasurable. Recoveries from samples of ripe fruit were high. It is argued that this differential recovery of fructose 2,6-bisphosphate undermines claims that the amount of this compound increases at the climacteric. When recoveries are taken into account, our data suggest that there is no major change in fructose 2,6-bisphosphate content during the onset of the climacteric in bananas.

Mycolic acid metabolic filiation and location in Mycobacterium aurum and Mycobacterium phlei

“…Structural and stereochemical data were obtained that suggest independent routes of formation of unsaturated and oxygenated mycolates [14], while the S configuration established for the chiral center occurring in methyl carbinols was in agreement with a biosynthetic relationship between oxomycolates and wax-ester mycolates [I 31.…”

“…This was substantiated by structural analogies between oxomycolates and dicarboxymycolates [7] and these similarities were extended to the stereochemistry of the methyl 0x0 group of oxomycolates [14] and of alcohols esterifying dicarboxymycolates [13].…”

“…More recently, the Baeyer-Villiger oxidation was supported by Yano et al [12], who showed that after incubation in the presence of "0 and degradation of wax-ester mycolate into dicarboxy acid and alcohol (Scheme l), only the oxygen atom of the alcohol (2-octadecanol or 2-icosanol according to the species) was labelled. But this experiment did not bring any evidence that oxidation takes place on the oxomycolic acid: it could occur before mycolic condensation [9, 131, on a nonhydroxylated long-chain (about c60) fatty acid precursor (meromycolic acid: R-COOH), or on a shorter one.Structural and stereochemical data were obtained that suggest independent routes of formation of unsaturated and oxygenated mycolates [14], while the S configuration established for the chiral center occurring in methyl carbinols was in agreement with a biosynthetic relationship between oxomycolates and wax-ester mycolates [I 31.The above proposals on mycolate biosynthesis are based on structural analogies between molecules and they need to be confirmed by metabolic evidence. At the present time, no cell-free system is available for such work, and it has to be performed on intact cells.…”

“…aurum (ATCC 23366) had a much more stable content of mycolic acids then M . phlei and oxomycolic acid was the major one [14], so variations in it were not always so easy to detect, because of the dilution of labelled compounds.…”

Trafficking pathways of mycolic acids: structures, origin, mechanism of formation, and storage form of mycobacteric acids

“…Their structures have been shown to be related to those of mycolic acids from the same species. For instance, keto and methoxyl groups were shown to occur in mycobacteric acids and mycolic acids isolated from M. tuberculosis (11); similarly, keto and wax functions were found in both types of fatty acids isolated from M. aurum (16). A series of shorter homologous fatty acids have been also isolated from triacylglycerols (TAGs) of a Nocardia species; these consist in C [35][36][37][38][39][40][41][42][43][44][45] fatty acids containing 3 and 4 double bonds as observed in nocardomycolic acids (17).…”