sphingolipid metabolism n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Sphingolipid metabolism PowerPoint Presentation
Download Presentation
Sphingolipid metabolism

Loading in 2 Seconds...

play fullscreen
1 / 34

Sphingolipid metabolism - PowerPoint PPT Presentation


  • 112 Views
  • Uploaded on

Sphingolipid metabolism. Starts with palmitoyl-CoA and serine, which is reduced and undergoes a transacylation and desaturation to yield ceramide (containing sphingosine; refer to figure 10-12) Uses UDP activated sugars, but not CTP activated head groups.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Sphingolipid metabolism' - bette


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
sphingolipid metabolism
Sphingolipid metabolism
  • Starts with palmitoyl-CoA and serine, which is reduced and undergoes a transacylation and desaturation to yield ceramide (containing sphingosine; refer to figure 10-12)
  • Uses UDP activated sugars, but not CTP activated head groups
role of sphingolipids
Role of sphingolipids
  • Abundant component of myelin sheath (25% in humans)
  • Also widely distributed in membranes of plants (use phytosphingosine), and lower eukaryotes (yeast)
  • These lipids are in a continuous state of turnover, defects in this metabolism leads to various diseases
however little is known about their specific biochemical function
However, little is known about their specific biochemical function
  • Gangliosides are receptors for specific agents such as influenza virus
  • Some gangliosides promote growth of neural tissue in cell cultyre
  • Biological signaling agents, possibly apoptosis as we will see in near future
fatty acid lipid membrane
Fatty acid  lipid  membrane
  • After lipids are synthesized in the ER, polar lipids are delivered to the Golgi apparatus, which serves as a clearinghouse sending specific lipids to specific targets using membrane vesicles
steroid metabolism
Steroid metabolism
  • Sterols (steroids) are class of lipids that are derivatives of a tetracyclic hydrocarbon
cholesterol is made from acetyl coa
Cholesterol is made from acetyl-CoA
  • Mevalonate formation is

the first stage of cholesterol

synthesis

acetate mevalonate
Acetate  Mevalonate
  • Catalyzed by thiolase, b-hydroxy-b-methylglutaryl-CoA (HMG-CoA) synthase and reductase
  • The reductase is the first committed step in this pathway; regulatory point
  • This last step is a four electron reduction
a momentary diversion
A momentary diversion:
  • Isoprenoids are

precursors for several

important biomolecules

regulation of cholesterol biosynthesis
Regulation of cholesterol biosynthesis
  • HMG-CoA reductase is a major target for regulation.
  • Hormonal regulation by insulin and glucagon
  • Ingestion of cholesterol inhibits endogenous cholesterol synthesis (control exerted at both transcriptional and translational levels)
  • Additional sophistication in vertebrates
lipids and proteins
Lipids and proteins
  • Proteins mediate lipid

transport between tissues

  • Proteins are also modified

by lipids

fate of cholesterol
Fate of cholesterol
  • Cholesterol is used by cells to decrease fluidity of cell membrane
  • Used in steroid hormone and bile salt biosynthesis
  • Cholesterol can also be exported from liver as bile acids, cholesteryl esters, or biliary cholesterol
    • Bile acids aid in digestion
    • Cholesteryl esters are transported to other other tissues to use cholesterol
bile acids are steroid derivatives with detergent properties
Bile acids are steroid derivatives with detergent properties
  • Emulsify dietary lipids
  • Secreted from liver, stored in gall bladder, passed through bile duct into intestine
  • Bile acids represent a major metabolic fate of cholesterol, accounting for more than half of the 800 mg/day of cholesterol metabolized (steroid hormones represent about 50 mg of cholesterol per day)
  • Bile acids are recycled through small intestine
cholesterol is the biosynthetic source of all steroid hormones
Cholesterol is the biosynthetic source of all steroid hormones
  • Five major classes of hormones
    • Progestins (regulate events during pregnancy and are precursors to all other steroid hormones)
    • Glucocorticoids (promote gluconeogenesis, and in certain doses suppress inflammation rxns)
    • Mineralocorticoids (regulate ion balance in kidney)
    • Androgens (male sexual characteristic development and maintenance)
    • Estrogens (female sexual characteristics development and maintenance)
what stands out about steroid hormone biosynthesis
What stands out about steroid hormone biosynthesis?
  • Role of cytochrome P450 and side chain cleavage in mitochondria
  • Multiple hydroxylations
  • Central role of pregnenolone
  • Mammalian cells lack capacity for complete degradation of steroids. Although a number of catabolic reactions occur, most are conjugated through their hydroxyl groups to glucuronate or sulfate, increasing solubility and allowing elimination through urine
other isoprenoid compounds
Other isoprenoid compounds:
  • Vitamin A, D, K, E
  • Terpenes – generic term for all compounds biosynthesized from isoprene precursors; hence all the molecules we have discussed today are terpenes.