Biosynthesis of Triglycerides- Microbial Nutrition.pptx

Biosynthesis of Triglycerides and sterols- Microbial Nutrition- Physiology

1. BIOSYNTHESIS OF TRIGLYCERIDES Presented by, K. Subbulexmi I M.Sc Microbiology Sri Paramakalyani college Alwarkurichi

2. 01. Introduction TABLE of contents 02. About Biosynthesis 03. Triglycerides 07. Storage in Adipose Tissues 09. Disorders of TG Metabolism 04. Structure 10. Clinical Significance 05. Biosynthesis of TG and different pathways of biosynthesis 08. Metabolisation and Utilization 11. Conclusion 06. Regulation of TG biosynthesis 12. References

3. Introduction The biosynthesis of triglycerides is a complex process by which living organisms create Triglycerides , also known as Triacylglycerols , from simpler molecules. Triglycerides are the main constituents of vegetable oils and animal fats and play a crucial role in energy storage and metabolism.

4. . What is Biosynthesis ? . . Biosynthesis is the process by which living organisms create complex molecules from simpler ones . It involves a series of enzyme-catalyzed chemical reactions that transform substrates into products , often requiring energy input. Biosynthesis occurs within cells and is essential for : 1 . Energy storage and metabolism 2 . Cell growth and maintenance 3 . Reproduction and development 4 . Response to environmental stimuli Biosynthesis can be divided into two main categories : 1 . Anabolism : The construction of complex molecules from simpler ones, often requiring energy input (e.g., protein synthesis, triglyceride synthesis ). 2 . Catabolism : The breakdown of complex molecules into simpler ones, often releasing energy (e.g., glycolysis, fatty acid oxidation).

5. TRIGLYCERIDES A  Triglyceride  (also TG, triacylglycerol, TAG, or  triacylglyceride ) is an ester derived from  glycerol  and three fatty acids . One such example of Triglyceride – derived from Glycerol + one molecule each of palmitic acid, oleic acid and stearic acid (the most abundant fatty acids in the biological world)  Triglycerides are the main constituents of body fat   in humans and other vertebrates, as well as vegetable fat. They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver , and are a major component of human skin oils.

6. STRUCTURE OF TRIGLYCERIDE: The structure of triglycerides consists of : Glycerol backbone: A three carbon sugar molecule (propane-1,2,3-triol) Has three hydroxyl (-OH) groups, one on each carbon atom Fatty acid chains: Long chains of carbon and hydrogen atoms (typically 14-24 carbon atoms ) a ttached to the glycerol backbone through ester bonds (-COO-) and that c an be saturated (no double bonds) or unsaturated (one or more double bonds) Ester bonds : Formed between the carboxyl (-COOH) group of a fatty acid and the hydroxyl (-OH) group of glycerol and create a stable and energy-rich bond

7. BIOSYNTHESIS OF TRYGLYCERIDES The intracellular site for the synthesis of Triglycerides is C ytosol . The building blocks of Triglycerides are Glycerol and Fatty Acids. Both of these have to be activated before being used for synthesis. The fatty acids are activated to acylCoA by the enzyme called Thiokinase . Glycerol is activated to Glycerol-3-phosphate by Glycerol kinase enzyme. Most tissues posses glycerol kinase and can use for Triglyceride synthesis. However, adipose tissue lacks Glycerol kinase . It can’t utilize the glycerol released from hydrolysis of triglycerides. In adipose tissue, Glycerol-3-phosphate is formed from glucose in the Glycoltic pathway . This is reduced to Glycerol-3-phosphate in adipocytes. Glycerol-3-phosphate is acylated to 1-acylglycerol-3-phosphate by Glycerol-3-phosphate acyl transferase .

8. BIOSYNTHESIS OF TRIGLYCERIDES Three main pathways for triacylglycerol biosynthesis are known: A B C T he   glycerol-3-phosphate pathway, The main biosynthetic route to triacyl glycerols is the  sn -glycerol-3-phosphate or Kennedy pathway Di – hydroxy acetone phosphate pathway, predominate in liver and adipose tissue, and a monoacyl glycerol pathway in the intestines Monoacyl glycerol pathway, MOGAT and DGAT enzymes

9. KENNEDY PATHWAY: The Kennedy pathway, also known as the glycerol phosphate pathway, is a major route for triglyceride synthesis in cells. It's named after Eugene Kennedy , who first described it in the 1950 s . The Kennedy pathway is a crucial mechanism for triglyceride synthesis, particularly in the liver and adipose tissue . It's regulated by various factors, including insulin, glucagon, and fatty acid availability.

10. K E N N E D Y P A T H W A Y

11. DIHYDROXYACETONE__-PHOSPHATE PATHWAY: In a second pathway for triacylglycerol biosynthesis, dihydroxyacetone -phosphate in peroxisomes or the endoplasmic reticulum can be acylated with fatty acid CoA esters by an acyltransferase to form 1-acyl dihydroxyacetone -phosphate , which is reduced by dihydroxyacetone -phosphate oxido-reductase to lysophosphatidic acid and can then enter the pathway above to triacylglycerols . In prokaryotes, the glycerol-3-phosphate pathway of triacylglycerol biosynthesis only occurs, but in yeast both glycerol-3-phosphate and dihydroxyacetone -phosphate can be the primary precursors, and synthesis takes place in both cytoplasmic lipid droplets and the endoplasmic reticulum. In plants, the main pathway is via glycerol-3-phosphate.

12. MONOACYLGLYCEROL PATHWAY In the enterocytes of intestines after a meal, up to 75% of the triacylglycerols are synthesized via a monoacylglycerol pathway . In this, 2-monoacyl- sn -glycerols and free fatty acids released from dietary triacylglycerols by the action of pancreatic lipase within the intestines are taken up by the enterocytes . There , the monoacylglycerols are first acylated by an acyl CoA: monoacylglycerol acyltransferase (MOGAT) and to some extent by DGAT1 with formation of  sn -1,2-diacylglycerols as the first intermediate in the process. Finally , acyl CoA:diacylglycerol acyltransferases ( DGAT1 and DGAT2) react with the  sn -1,2-diacylglycerols to produce T riacylglycerols , but any  sn ‑2,3‑diacylglycerols formed are esterified relatively slowly by these enzymes.

13. Regulation of Triglyceride Biosynthesis Hormonal Regulation Insulin and glucagon play a crucial role in controlling the rate of triglyceride synthesis by modulating the activity of key enzymes involved in the process Substrate Availability The availability of substrates like fatty acids and glycerol-3-phosphate can directly influence the rate of triglyceride formation, as they are the building blocks of the triglyceride molecule Feedback Mechanisms Triglyceride biosynthesis is also subject to feedback regulation, where the end-product can inhibit the activity of enzymes involved in its own production. Transcriptional Control The expression of genes encoding key enzymes in the triglyceride biosynthesis pathway can be regulated by transcription factors, allowing for long-term adaptations in triglyceride production .

14. Triglyceride Storage in Adipose Tissue Lipid Droplet Formation Excess triglycerides are packaged into specialized lipid droplets within adipocytes , the primary storage site for triglycerides in the body Adipose Tissue Depot Triglycerides are primarily stored in the adipose tissue, which serves as a crucial energy reserve and insulation for the body. Triglyceride Mobilization During periods of energy demand, the triglycerides stored in adipose tissue can be broken down through lipolysis, releasing fatty acids for use as fuel

15. Triglyceride Mobilization and Utilization 1 2 3 Lipolysis in Adipose Tissue Triglycerides stored in adipose tissue are broken down into fatty acids and glycerol through the process of lipolysis, mediated by lipase enzymes. Transport in the Bloodstream The released fatty acids are then transported in the bloodstream, bound to albumin or packaged into lipoproteins, to be utilized by peripheral tissues . Tissue Uptake and Utilization The fatty acids are taken up by cells in tissues like muscle, liver, and heart, where they can be used as a source of energy through beta-oxidation.

16. Continuation….. Some OTHER WAYS OF TRIGLYCERIDE UTILIZATION: Cell membrane structure: Triglycerides are incorporated into cell membranes, helping maintain fluidity and structure. Hormone production : Triglycerides are converted into hormones like cholesterol, which is necessary for steroid hormone production. Absorption of vitamins : Triglycerides facilitate the absorption of fat-soluble vitamins (A, D, E, and K) in the intestine. Skin and hair health: Triglycerides help maintain skin and hair health by providing moisture and shine. Inflammation reduction: Triglycerides have anti-inflammatory properties, helping reduce inflammation in the body . Brain function : Triglycerides are involved in brain function and development, particularly in myelin formation. 1. 2. 3. 4. 5. 6.

17. Disorders of Triglyceride Metabolism Hypertriglyceridemia Elevated levels of triglycerides in the blood, which can increase the risk of cardiovascular disease and pancreatitis . Familial Chylomicronemia Syndrome A rare genetic disorder characterized by severe hypertriglyceridemia due to the inability to properly metabolize chylomicrons. Metabolic Syndrome A cluster of conditions, including high triglycerides, that increase the risk of heart disease, stroke, and type 2 diabetes . (Normal– <150 mg/dl Borderline high- 150 to 199 mg/dl High- 200 to 499 mg/dl Very high- 500 mg/dl or above)

18. Conclusion The biosynthesis of triglycerides is a multi-step process involving fatty acid synthesis, glycerol-3-phosphate production, and esterification reactions, resulting in the formation of triglycerides, a crucial energy storage molecule in the body, primarily synthesized in the liver and adipose tissue.

19. REFERENCES: https:// www.lipidmaps.org/resources/lipidweb/lipidweb_html/lipids/simple/tag2/index.htm https://byjus.com/chemistry/triglyceride-structure / https:// www.slideshare.net/slideshow/triglycerides-65579507/65579507#4 https:// www.slideshare.net/slideshow/biosynthesis-of-triacylglycerol/249847997#21 https:// en.wikipedia.org/wiki/Triglyceride https:// www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/triglycerides/art-20048186 https:// img.freepik.com/premium-photo/close-up-human-body-with-futuristic-generative-ai_771703-2437.jpg https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_(Biological_Chemistry)/ Lipids/Glycerides/Triglycerides https:// study.com/learn/lesson/triacylglycerol-structure-function-what-is-triacylglycerol.html