Endogenous pathway for lipid metabolism:
(the rate limiting setp in cholesterol biosynthesis.
Our results have interesting implications for evolution of enzymes for SQ biosynthesis. The pathway in bacteria begins with cyclopropanation of FPP to give PSPP. It is likely that PSPPase activity arose from ubiquitous chain elongation enzymes (PF00348) in the isoprenoid synthase superfamily. There is precedent for the independent emergence of cyclopropane-forming activity in chrysanthemyl diphosphate synthase from a FPPase in plants as recently as ∼50 million years ago (MYA). Eukaryotic SQase, which synthesizes PSPP from FPP in the absence of NADPH, also converts PSPP to HSQ. This observation, along with documented promiscuous activities for yeast SQase, supports a scenario for evolution of PSPPase from an ancestral chain elongation enzyme and of HSQase from PSPPase. In this scenario, the HSQ reductase activity in HpnE, which is a necessary step in the biosynthesis of hopanoid metabolites that insert properly into membrane, evolved independently from a protein in the flavin-dependent amino oxidase family.
statins block the pathway for synthesizing cholesterol in ..
There is a recent report of PSPPase activity in the colonial eukaryotic photosynthetic alga race B. has a gene for SQase (BSS) and three “SQase-like (SSL)” genes. The BSS protein converts FPP to SQ like other eukaryotic SQases. SSL1 converts FPP to PSPP, SSL2 catalyzes an NADPH-dependent reductive rearrangement/reduction of PSPP to SQ, and SSL3 catalyzes the NADPH-dependent reductive rearrangement of PSPP to botryococcene (BO), a triterpene isomer of SQ. SQ, BO, and their methylated derivatives are pumped into a translucent membrane surrounding individual cells in the colony, where they accumulate to 30–86% of the dry weight of the algal mass and provide flotation for maximal exposure of the organism to sunlight. BSS and the three SSL genes are estimated to have separated from a common ancestor ∼500 MYA. A brief phylogenetic analysis of the four genes places them firmly within a group of other eukaryotic SQase genes in fungi, plants, and animals (). Most likely, the PSPPase evolved from a eukaryotic SQase to facilitate regulation of the flux of FPP into sterol biosynthesis independently from the flux into biosynthesis of the massive amounts of methylated SQ and BO required for flotation. In contrast, in both Gram-positive and Gram-negative bacteria is distantly related to eukaryotic SQases, consistent with an ancient common ancestor for the bacterial and eukaryotic enzymes.
Cholesterol Biosynthesis from ..
Thatacidic lipid was later shown to be a universal component of photosynthetictissues.
Hirsch J reported the reversed-phase separation of non polar lipids on a columnof polymerized vegetable oil (Factice) ().
Klenk E et al.
is the terminal enzyme in the pathway of cholesterol biosynthesis
reported the reversed-phase separation of fatty acids by acomplex two-dimensional TLC employing a catalytic hydrogenationon the plate ().
First description of a direct titration method for analytical hydrogenation todetermine precisely the unsaturation of lipids ().
Discovery of O-amino acid (alanyl and lysyl) esters of phosphatidylglycerol in agram-positive bacteria ().
The first GLC analysis of natural triglycerides from milk fat was reported ().
Hematoside, the ganglioside of horse erythrocytes, is the first ganglioside(GM3) whose structure was elucidated ().
The complete structure of sulfatide (sulfated galactosylceramide) was elucidatedincluding the position of the sulfate group attached to the C3 of galactose ().
Methyl jasmonate was discovered in flowers of jasmine and was shown to be afragrant component in the essential oil from these flowers ().
Discovery of diether-type phospholipids in a an extremely halophilic bacteria () ().
First demonstration of the presence of 2-aminoethylphosphonic acid and itsglycerol ester in lipid extractsof the sea anemone, ().