Pristanic

Pristane is an alkane that is present to the extent of about 14% in shark liver oil. Its lUPAC name is 2,6,10,14-tetramethylpentadecane. Write its structural formula. 

FIGURE 24.26 Branched-chain fatty acids are oxidized by o -oxidation, as shown for phytanic acid. The product of the phytanic acid oxidase, pristanic acid, is a suitable substrate for normal /3-oxidation. Isobutyryl-CoA and propionyl-CoA can both be converted to suc-cinyl-CoA, which can enter the TCA cycle. 

Identification becomes more difficult in the case of isoparaffins since many structural isomers are possible with increasing carbon number. Nevertheless, all possible isoalkanes from through have been found in crude oils, along with several isomers of and some of Many isoprenoids (e.g., pristane and phytane) which serve as biomarkers to the genesis of petroleum have been detected in significant... 

The degradation of pristane in microcosms and in enrichment cultures (Bregnard et al. 1997). 

Bregnard TP-A, A Haner, P Hohener, J Zeyer (1997) Anaerobic degradation of pristane in nitrate-reducing microcosms and Qmichme,ntca t jxe. Appl Environ Microbiol 63 2077-2081. 

McKenna EJ, RE Kallio (1971) Microbial metabolism of the isoprenoid alkane pristane. Proc Natl Acad Sci USA 68 1552-1554. 

The biodegradation of n-alkanes and the pathways whereby it is accomplished are well established. The range of componnds includes branched-chain compounds such as pristane... 

Refsum s disease. This disorder, first described nearly 60 years ago, was recently been shown due to a defect in the enzyme phytanoyl-CoA hydroxylase. Phytanic acid is a 3-methyl fatty acid that because of this methyl group cannot be oxidized directly. It is degraded by a peroxisomal a-oxidation to pristanic acid, a 2-methyl fatty acid which can be degraded by P-oxidation. The principal clinical features of Refsum s disease are progressive polyneuropathy, retinal degeneration, hearing loss, cardiomyopathy and ichthyosis, beginning in late childhood or later. 

Racemase deficiency. The biological role of 2-methyl-acyl-CoA racemase has only recently been clarified. This peroxisomal enzyme is essential for certain steps of the oxidation of phytol and bile acid derivatives, which are stereospecific. Biochemically there is accumulation of pristanic acid and C27 bile acid intermediates. Clinical symptoms may include adult-onset peripheral neuropathy, pigmentary degeneration of the retina and liver disease [ 13]. 

The isoprenoid hycrocarbons pristane and phytane (derived from the phytol side chain of chlorophyll), as well as porphyrins, have been detected in organic extracts of the Nonesuch Shale of 1.1 billion year age [23]. Their presence points to the existence of photosynthetic pigments in the Precambrian era, but it is also possible that these extractable substances could have been contributed to the rock at a later time. However, in this instance contamination appears to be less likely on account of the large abundance of organic material in this shale. 

Pristane (2,6,10,14-tetramethylpentadecane) is a mineral oil known to induce arthritis, a disease also referred to as pristane-induced arthritis (PIA) [58], Susceptibility to PIA is MHC-haplotype dependent, in that DBA/1 (H2q) mice are susceptible whereas DBA/2 (H2d) are not, and is accompanied by a broad spectrum of autoantibodies, including anti-Rheuma Factor (RF), anti-collagen and antibodies to heat shock proteins (HSP). PIA is clearly immune dependent since nu/nu mice and irradiated mice do not develop PIA. PIA involves polyclonal T cell activation [59], particularly CD4+ cells [58], Intriguingly, mice can be protected from developing PIA by HSP65-specilic CD4+ Th2 cells [60],... 

Wooley, P.H., and Whalen, J.D. Pristane-induced arthritis in mice. III. Lymphocyte phenotypic and functional abnormalities precede the development of pristane-induced arthritis. Cell. Immunol., 138, 251, 1991. 

Wooley, P.H. et al., Pristane-induced arthritis in mice. V. Susceptibility to pristane-induced arthritis is determined by the genetic regulation of the T cell repertoire. Arthritis Rheum., 41,2022, 1998. 

Beech, J. T. et al., CD4+ Th2 cells specific for mycobacterial 65-kilodalton heat shock protein protect against pristane-induced arthritis. J. Immunol., 159, 3692, 1997. 

Priority-based Assessment of Food Additives (PAFA) program, 23 667 Priority pollutants, 9 443 Prior sanctioned substances, 12 34 Pristane, 18 592... 

Figure 7.12 Potential biomarkers in bitumen the isoprenes (a) pristane (Ci9H40) and (b) phytane (C2oH42), and (c) the hopane 17o (H), 21/3(H)-pentakishomohopane (22R).

Of particnlar significance in the study of petroleum weathering are the biomarker molecules (e.g., pristane, phytane, the hopanes and steranes). Historically, the biomarkers have been employed as crude oil signatures in prospecting and characterization. More recently, such molecules have also been employed in the environmental field, both for the determination of pollutant source and estimation of the degree of weathering. 

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