Fatty acid hydroperoxides biotransformation by potato tuber cell-free extracts

Abstract

SummaryCleavage of 13-HPOD, 13-HPOT, 9-HPOD and 9-HPOT by potato tuber cell-free extracts was investigated. 13-HPOD and 13-HPOT enzymes were degraded almost completely while 9-HPOD and 9-HPOT were partially transformed. GC-MS analysis of the volatile compounds formed during the reactions revealed that (Z)-3 hexenal, (E)-2-hexenal, pentenols and dimers of pentene were obtained from 13-HPOT while from 13-HPOD hexanal and pentan-1-ol were formed. No volatile was found when 9-HPO isomers were used as substrate, but colneleic acid was produced. When Triton X-100 was omitted in the extraction buffer, only pentenols and dimers of pentene were identified from 13-HPOT and pentan-1-ol from 13-HPOD. Our results reveal that potato tubers that contain Lox, which forms mainly 9-HPO, are able to metabolise the four HPO isomers. Moreover, 13-HPO cleaving activities are due to two distinct enzymatic systems based on, respectively, homolytic and heterolytic mechanisms. The fact that oxygenation of reaction medium dramatically decreases the amount of product resulting from homolytic cleavage strengthens the hypothesis of an anaerobic reaction due to Lox.Key words: aldehyde -fatty acid hydroperoxide -heterolytic and homolytic hydroperoxide cleavage -hydroperoxide lyase -potato tuber -Solanum tuberosum L.Abbreviations: GC-MS = gas-chromatography mass spectrometry. -HPLC = high performance liquid chromatography. -HPO = fatty acid hydroperoxide. -13-HPOT = 13 hydroperoxide of linolenic acid. -13-HPOD = 13 hydroperoxide of linoleic acid. -9-HPOT = 9 hydroperoxide of linolenic acid. -9-HPOD = 9 hydroperoxide of linoleic acid. -Lox = lipoxygenase *

Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.)

“…As we previously described [30], because potato tubers don't contain large amount of HPO lyase, HPOs can be extracted and quantified without reduction to the corresponding alcohols. Omitting the reduction step is more rapid and allows separate determination of hydroxy fatty acids that may be formed in the plant.…”

“…Colneleic acid is clearly involved in plant defence against pathogens [6,14] and is also an inhibitor of LOX activity [33], but this work is the first indication for a role of colneleic acid during the normal life cycle of the tuber, and for a potential role of colneleic acid in sprout development. It is unlikely that the 9-oxo-nonanoic acid methyl ester in the extracts was formed by the action of HPO lyase on 9-HPOD and HPOT, because it has been demonstrated that potato tuber HPO lyase is specific for 13-HPOD and HPOT [30,34], and the tubers contained little 13-HPOD and HPOT. Moreover, HPO lyase activity rapidly drops to zero during tuber storage [30].…”

“…It is unlikely that the 9-oxo-nonanoic acid methyl ester in the extracts was formed by the action of HPO lyase on 9-HPOD and HPOT, because it has been demonstrated that potato tuber HPO lyase is specific for 13-HPOD and HPOT [30,34], and the tubers contained little 13-HPOD and HPOT. Moreover, HPO lyase activity rapidly drops to zero during tuber storage [30]. Since 9-oxononanoic acid is present even after 210 days of aging, we postulate that it is not formed by HPO lyase, but that it is a degradation product originating from colneleic acid.…”

Biotechnology for the production of essential oils, flavours and volatile isolates. A review.

“…Traces of benzoin produced from benzaldehyde [239] Cell-free extract Potato tuber Hexenals, hexanal, pentenals, pentenol were formed from fatty acid hydroperoxides [240] Cutinase, immobilized…”