Stach biosynthesis

Stach biosynthesis

1. SYNTHESIS AND ACCUMULATION OF STARCH AND MOBILIZATION OF STARCH DURING GERMINATION BASIC BIOCHEMISTRY BCM.501(2+1) PRESENTED BY : kiran dasanal PALB7319 Jr. MSc ( agri ) seed science and technology 22/05/2018 1 WELCOME

2. CONTENTS Importance of starch Composition of starch Synthesis of starch ADPG-PP enzyme Enzymes limiting starch synthesis Mobilization of starch in cereals Mobilization of starch in pulses 22/05/2018 KIRAN DASANAL PALB7319 2

3. IMPORTANCE OF STARCH Most significant carbon reserve in plants (i.e. amount made & distribution) Major component of crop plant yield in the world Major source of calories in the human diet Important raw material for industrial processes (e.g. potato & maize). A major component of food, feed and cloth. Starting material for ethanol production. Broad applications in the paper and textile industries. Owing to t heir biodegradable and renewable nature, they are increasingly being considered as an environmentally-friendly alternative to the use of synthetic additives. 22/05/2018 3 KIRAN DASANAL PALB7319

4. FACTS ABOUT STARCH Starch, a polysaccharide , is synthesized in the chloroplast. Starch formation occurs in plastids. Starch granules are classified as transitory or reserve. Transitory starch granules accumulate for only a short period of time before they are degraded, e.g. a)Starch forms in leaf chloroplasts during the day. b)hydrolyzed and transported to other plant parts at night as simple sugar. Reserve starch, an energy storage for germination, a major component of food and feed, and an industrial starting material, is formed in amyloplasts . 22/05/2018 4 KIRAN DASANAL PALB7319

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7. CONT….. Starch id widely found in Two forms: α - Amylose α - Amylopectin . α - amylose ; is a long chain polymer, where the Glucose residues are linked by α ( 1 4) Glycosidic bonds. It is a straight chain compound. It does not dissolve in water and with Iodine it gives Blue color. 22/05/2018 7 KIRAN DASANAL PALB7319

8. CONT…. α - amlopectin : It is a ploymer of having branched chain. The branching in starch occurs for every 22 - 25 Glucose residues. It is branch chain having α ( 1 4), α ( 1 6) glycosidic bonds. Amylopectin gives Reddish Violet color with Iodine. 22/05/2018 8 KIRAN DASANAL PALB7319

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10. About ADPG-PP enzyme It is a heterotetramer ( α 2 β 2) has two large units(regulatory properties) and two small units(catalytic properties). Activity of this enzyme linked to starch accumulation. It is a rate of limiting enzyme 22/05/2018 10 KIRAN DASANAL PALB7319

11. Key enzymes limiting the starch synthesis Brittle-2: mutant of ADPG- PP,it removes the small sub unit ie catalytic activity is last. Shrunken mutant(Sh-2): mutant for regulatory property ie large sub unit of ADPG-PP. Sugery mutant: sucrose synthase enzyme is knocked off.sucrose get accumulated in the cytosol of cell. Wrinkled mutant: only accumulation of amylose not amylopectin . 22/05/2018 11 KIRAN DASANAL PALB7319

12. Days after fertilization 22/05/2018 12 KIRAN DASANAL PALB7319

13. UTILIZATION OF SEED RESERVES DURING SEED GERMINATION 22/05/2018 13 KIRAN DASANAL PALB7319

14. MOBILIZATION OF STARCH DURING GERMINATION In endosperm of cereals, starch degradation is takes place in a non living tissue—effectively in an acidic, apoplastic environment in which no intracellular or intercellular compartmentation exists. Amyloplast envelope and the plasma membrane disintegrate. Degradation of starch granule catalyzed by α -amylase enzyme synthesized in scutellum . Later α -amylase enzyme synthesized in aleuron layer. 22/05/2018 14 KIRAN DASANAL PALB7319

15. CONT…. Maltose is the major product of hydrolysis and further broken into glucose by α - glucosidase (maltase) enzyme present in the embryo ad aleuron layer. Finaly scutellum is a modified single cotyledon located between the endosperm and the embryo. The epithelial cells of scutellum facilitate exchange between the embryo and the endosperm. Glucose is absorbed from the endosperm and converted to sucrose in scutellum and transported to embryo. 22/05/2018 15 KIRAN DASANAL PALB7319

16. BREAKDOWN OF STARCH IN CEREALS 22/05/2018 16 KIRAN DASANAL PALB7319

17. BREAKDOWN OF STARCH IN PULSES DURING GERMINATION In legumes,the hydrolysis of cotyledonary reserves commences after emergence and elongation of the radicle . The plastid envelope is believed to disintegrate prior to germination so that degradation occurs within the cytosol . The initial slow phase is associated with activity of starch phosphorylase . The more rapid degradation phase coincides with α and β amylase activity. 22/05/2018 17 KIRAN DASANAL PALB7319

18. Cont…. Later attacks the starch granules and cause to change the starch strcture . Then the glucan water dikinase enzyme react with glucan in presence of ATP and water it adds the β -phosphate group of ATP to either the 3-or the6-carbon of a glucosyl residue of amylopectin . Glucan + ATP+ water GWD Glucan -p +AMP+ Inorganic phosphate 22/05/2018 18 KIRAN DASANAL PALB7319

19. BREAKDOWN OF STARCH IN PULSES 22/05/2018 19 KIRAN DASANAL PALB7319

20. CONT….. The amyloplast mebrane disintegrates so that starch degradation is catalysed by cytosolic enzymes. sucrose synthesized from starch is exported from the starch-storing cells to the growing root and shoot of the seedling. 22/05/2018 20 KIRAN DASANAL PALB7319

21. REFERENCES Seed science and technology by N C SINGHAL. Class notes of Dr uma shanker sir. 22/05/2018 KIRAN DASANAL PALB7319 21

22. THANK YOU 22/05/2018 22 KIRAN DASANAL PALB7319