Reconstitution of Plant Alkane Biosynthesis ..

Improving alkane synthesis inEscherichia colivia …

Two transcribed genes encoding 3-ketoacyl-CoA thiolase [(EC 2.3.1.16) Thiolase III], one of the peroxisomal thiolase isozymes, of n-alkane-utilizable yeast, Candida tropicalis, were isolated. Restriction maps of these two genes were very similar. Each of the genes had only one open reading frame consisting of 1224 bp corresponding to 408 amino acid residues. The nucleotide sequences of another thiolase isozyme in peroxisomes of C. tropicalis, acetoacetyl-CoA thiolase (Thiolase IA and IB), have been already determined (Kurihara et al., Eur. J. Biochem., 210, 999-1005, 1992). The amino acid sequences of these peroxisomal thiolase isozymes (Thiolases I and III) showed 35% homology. The regulation of biosynthesis of these thiolases in C. tropicalis was compared by RNA and Western blotting analyses. The results revealed that the biosynthesis of Thiolase III in C. tropicalis was strongly induced in a medium containing butyrate or alkanes as a carbon source and a peroxisome proliferator, while Thiolase I was constitutively expressed even in a medium with glucose or acetate, although a slight induction was observed at the levels of transcription and translation in the medium containing butyrate or alkanes. Thus, the regulations of biosyntheses of Thiolases I and III were found to be quite different, in spite of the enzymes in the final step of the peroxisomal fatty acid β-oxidation system.

Improving alkane synthesis in ..


This chain type is frequently found in several lipid forms, either isolated or combinedwith other chemical structures. A series of long-chain methylated alkanes (more than 23carbon atoms), saturated or with one double bond, were identified in settlingparticles and surface sediments from Japanese lakes and were shown to beproduced by planktonic bacteria being thus useful molecular markers (). Laboratory experiments havedemonstrated that -alkanes up to C35 may be formed in the laboratoryunder hydrothermal conditions (Fischer-Tropsch-type reactions) from formic acidor oxalic acid ().These results support the theory of the origin of life in hydrothermal systems.
Methoxyalkanes have been identified on bodies or silk of spiders :1-methoxy-16,20,24,28-tetramethylhentriacontane and1-methyl-2,24-dimethyloctacosane ().
It must be noticed that highly branched and unsaturated (2-5 double bonds)isoprenoids are widespread components in marine sediments (review by). The identification of C25 and evenof C30 highly branched isoprenoid alkenes in diatoms () have clearly established that they are the source ofthese compounds found in sediments.
Among the saturated isoprenoids found in geological sediments and oils, the mostfrequent are pristane (2,6,10,14-tetramethylpentadecane) and phytane (2,6,10,14-tetramethylhexadecane). Both compounds can be generateddiagenetically from the phytol side chain of chlorophyll. Pristane may alsoderive from the side chain of tocopherols while phytane is also generated byArchaea.

AB - The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor.


Microbial biosynthesis of alkanes

The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor.

Biosynthesis of alkane-2,3-diols: Enzymatic reduction of …

AB - Two transcribed genes encoding 3-ketoacyl-CoA thiolase [(EC 2.3.1.16) Thiolase III], one of the peroxisomal thiolase isozymes, of n-alkane-utilizable yeast, Candida tropicalis, were isolated. Restriction maps of these two genes were very similar. Each of the genes had only one open reading frame consisting of 1224 bp corresponding to 408 amino acid residues. The nucleotide sequences of another thiolase isozyme in peroxisomes of C. tropicalis, acetoacetyl-CoA thiolase (Thiolase IA and IB), have been already determined (Kurihara et al., Eur. J. Biochem., 210, 999-1005, 1992). The amino acid sequences of these peroxisomal thiolase isozymes (Thiolases I and III) showed 35% homology. The regulation of biosynthesis of these thiolases in C. tropicalis was compared by RNA and Western blotting analyses. The results revealed that the biosynthesis of Thiolase III in C. tropicalis was strongly induced in a medium containing butyrate or alkanes as a carbon source and a peroxisome proliferator, while Thiolase I was constitutively expressed even in a medium with glucose or acetate, although a slight induction was observed at the levels of transcription and translation in the medium containing butyrate or alkanes. Thus, the regulations of biosyntheses of Thiolases I and III were found to be quite different, in spite of the enzymes in the final step of the peroxisomal fatty acid β-oxidation system.